Add additional ProdCon updaters pointed at recent 2.1.1 build

[dagood]

Upgrades buildtools to get new updaters implemented in dotnet/buildtools#2047 and configures them, pointing at the recent 2.1.1 build.

I'm planning on porting the buildtools change from master to 2.1 once this gets merged, then porting this PR to source-build 2.1.

Ideally I'd use a master manifest rather than 2.1.1, but we don't have one. The source-build master appears to still be on 2.1.0 for now so this is still an upgrade.

#534

[eerhardt]

Does this need to be $(OfficialBuildId) ?

[dagood]

Oops, yep. As-is this ends up creating a build id updater for every project unconditionally.

[dagood]

In this PR I updated buildtools to master to get the new updaters, but this is incompatible with the 2.1.1 CoreFX commit. I reverted the BuildTools update to see if the submodule updates go through CI other than that.

Once dotnet/buildtools#2063 is through, we'll have a 2.1 BuildTools that includes the updaters.

We're also at an awkward place where #589 will update the Core repos to master soon. There aren't any ProdCon master builds to point at, so it will become impossible to meaningfully test auto-update config changes in source-build master.

[dagood]

@crummel, looks like I also ran into the reason we need net46 builds. (#592)

/mnt/j/workspace/dotnet_source-build/master/Ubuntu16.04_Release_prtest/src/sdk/src/Tasks/Microsoft.NET.Build.Extensions.Tasks/Microsoft.NET.Build.Extensions.Tasks.csproj :
error NU1202: Package Microsoft.Build.Framework 15.7.179 is not compatible with net46 (.NETFramework,Version=v4.6).
Package Microsoft.Build.Framework 15.7.179 supports: netstandard2.0 (.NETStandard,Version=v2.0) 
[/mnt/j/workspace/dotnet_source-build/master/Ubuntu16.04_Release_prtest/src/sdk/sdk.sln] [/mnt/j/workspace/dotnet_source-build/master/Ubuntu16.04_Release_prtest/repos/sdk.proj]

I'll revert the upgrade entirely for now, and just get the configuration in.

Edit: The port of the new updaters to BuildTools 2.1 is done. I updated to that version so the auto-update configuration won't immediately fail because of the updater types not existing.