Set AlwaysExpanded=True will cause CommandBarFlyout clipped when closing

[zhuxb711]

Describe the bug
If I change PrimaryCommand and close CommandBarFlyout, it will clip itself.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Set AlwaysExpaned = True
2. Change PrimaryCommand to hidden one
3. Close CommandBarFlyout

Expected behavior
Should close itself like it used to be.

Screenshots
I click "Copy" twice and it work well.
But if primary command changed and AlwaysExpanded is set to True. Then I found the bug.

Version Info

NuGet package version:
2.6.0-prerelease.210405001

Windows app type:

UWP	Win32
Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context
Example code:

        <muxc:CommandBarFlyout x:Name="FileFlyout"
                               AlwaysExpanded="True"
                               Placement="RightEdgeAlignedTop">
            <AppBarElementContainer x:Name="FileStandardBar">
                <StackPanel Orientation="Horizontal">
                    <AppBarButton Icon="Copy"/>
                    <AppBarButton Icon="Cut" />
                    <AppBarButton Icon="Delete"/>
                    <AppBarButton Icon="Rename" />
                    <Border Background="Transparent"
                            Padding="12"
                            PointerEntered="ColorTag_PointerEntered">
                        <Viewbox>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB52;" />
                        </Viewbox>
                    </Border>
                </StackPanel>
            </AppBarElementContainer>
            <AppBarElementContainer Visibility="{x:Bind FileStandardBar.Visibility, Mode=TwoWay, Converter={StaticResource InverseConverter}}">
                <StackPanel Orientation="Horizontal">
                    <AppBarButton Name="UnTag">
                        <AppBarButton.Icon>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB51;" />
                        </AppBarButton.Icon>
                    </AppBarButton>
                    <AppBarButton Foreground="Orange">
                        <AppBarButton.Icon>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB51;" />
                        </AppBarButton.Icon>
                    </AppBarButton>
                    <AppBarButton Foreground="GreenYellow">
                        <AppBarButton.Icon>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB51;" />
                        </AppBarButton.Icon>
                    </AppBarButton>
                    <AppBarButton Foreground="Yellow">
                        <AppBarButton.Icon>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB51;" />
                        </AppBarButton.Icon>
                    </AppBarButton>
                    <AppBarButton Foreground="#409EFE">
                        <AppBarButton.Icon>
                            <FontIcon FontFamily="{ThemeResource SymbolThemeFontFamily}"
                                      Glyph="&#xEB51;" />
                        </AppBarButton.Icon>
                    </AppBarButton>
                    <Border Background="Transparent"
                            Padding="12"
                            PointerEntered="ColorBarBack_PointerEntered">
                        <Viewbox>
                            <SymbolIcon Symbol="Back" />
                        </Viewbox>
                    </Border>
                </StackPanel>
            </AppBarElementContainer>
            <muxc:CommandBarFlyout.SecondaryCommands>
                  <!-- Add some secondarycommand here-->
            </muxc:CommandBarFlyout.SecondaryCommands>
</muxc:CommandBarFlyout>

[StephenLPeters]

@teaP FYI

[ranjeshj]

@StephenLPeters does this repro after your animation updates ?

[github-actions]

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