(GH-883) Wait Up to 15 Seconds for Process Exit

Even though `$process.WaitForExit()` has identified that the process
has exited, it appears that the process may be performing some final
cleanup as the exit code is still null when it is passed to
`Set-PowerShellExitCode`. Allow the process to take up to 15 seconds to
fully exit so that it has cleaned up. In the case of 7zip, ensure that
it has ample time to finish extracting after it has indicated that it
has completed the extraction and is exiting.

src/chocolatey.resources/helpers/functions/Get-ChocolateyUnzip.ps1

@@ -167,11 +167,16 @@ param(
   Unregister-Event -SourceIdentifier "LogErrors_ChocolateyZipProc"
 
   # sometimes the process hasn't fully exited yet.
-  Start-Sleep 1
+  for ($loopCount=1; $loopCount -le 15; $loopCount++) { 
+    if ($process.HasExited) { break; }
+    Write-Debug "Waiting for 7z.exe process to exit - $loopCount/15 seconds"; 
+    Start-Sleep 1; 
+  }
 
   $exitCode = $process.ExitCode
-  Set-PowerShellExitCode $exitCode
   $process.Dispose()
+
+  Set-PowerShellExitCode $exitCode
   Write-Debug "Command ['$7zip' $params] exited with `'$exitCode`'."
 
   if ($zipExtractLogFullPath) {

src/chocolatey.resources/helpers/functions/Start-ChocolateyProcessAsAdmin.ps1

@@ -206,7 +206,11 @@ Elevating Permissions and running [`"$exeToRun`" $wrappedStatements]. This may t
   Unregister-Event -SourceIdentifier "LogErrors_ChocolateyProc"
 
   # sometimes the process hasn't fully exited yet.
-  Start-Sleep 1
+  for ($loopCount=1; $loopCount -le 15; $loopCount++) { 
+    if ($process.HasExited) { break; }
+    Write-Debug "Waiting for process to exit - $loopCount/15 seconds"; 
+    Start-Sleep 1; 
+  }
 
   $exitCode = $process.ExitCode
   $process.Dispose()
@@ -218,7 +222,7 @@ Elevating Permissions and running [`"$exeToRun`" $wrappedStatements]. This may t
   } else {
     $chocoSuccessCodes = @(0, 1605, 1614, 1641, 3010)
     if ($chocoSuccessCodes -notcontains $exitCode) {
-      Write-Warning "Exit code '$exitCode' was considered valid, but not as a choco success code. Returning 0"
+      Write-Warning "Exit code '$exitCode' was considered valid by script, but not as a Chocolatey success code. Returning '0'."
       $exitCode = 0
     }
   }