Fix deploy to GCE

[ILMTitan]

• Remove app_offline.htm. It was not playing well with IIS Express (not sure why).
• Add <PublishWithAspNetCoreTargetManifest>false</...> to 2.x Project files. Fixes this deployment error.
• Fix showing the output for the GCE deploy. Running the build was hiding it again. Move the show after the build.
• Retry a failed deploy build once. The deploy will sometimes not be able to delete a dll the first time, especially when switching deployed projects.

[codecov[bot]]

Codecov Report

Merging #1045 into master will increase coverage by 0.05%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1045      +/-   ##
==========================================
+ Coverage   48.12%   48.17%   +0.05%     
==========================================
  Files         477      477              
  Lines       11608    11613       +5     
==========================================
+ Hits         5586     5595       +9     
+ Misses       6022     6018       -4

Impacted Files	Coverage Δ
...ension/PublishDialog/Steps/Gce/GceStepViewModel.cs	73.33% <ø> (+2.11%)	:arrow_up:
...leCloudExtension/Deployment/WindowsVmDeployment.cs	100% <100%> (ø)	:arrow_up:

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[ILMTitan]

PTAL