Porting fixes to #2792 and #2798 to v0.38

[iwankgb]

Porting of recent fixes applied to master.

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[iwankgb]

@Creatone can you add a consent comment, please?

[Creatone]

@googlebot I consent.

[bobbypage]

Why is the libimpctl dockerfile change needed to be cherrypicked? That seems more like a feature rather than a bug fix, so I think that would makes more sense for the next minor version instead.

[iwankgb]

@bobbypage it shouldn't have been, you are completely right :)

[bobbypage]

@iwankgb np, thanks for putting the cherrypick together!

[bobbypage]

https://github.com/google/cadvisor/releases/tag/v0.38.8 has been cut with this included.