nuget.exe push timeout needs a better error message

[maartenba]

nuget.exe push NuGetTestPackage.1.0.0.nupkg -ApiKey ... -Timeout 1
Pushing NuGetTestPackage.1.0.0.nupkg to 'https://www.nuget.org/api/v2/package'...
  PUT https://www.nuget.org/api/v2/package
A task was canceled.

"A task was canceled." should probably be "Push timeout expired." or similar.

[spadapet]

Dupe of: #2199
Here's the committed pull request: NuGet/NuGet.Client#442