Add -sweep-allow-failures to TeamCity param

[c2thorn]

Let's try using this:
https://github.com/hashicorp/terraform-plugin-sdk/blob/master/CHANGELOG.md#120-october-25-2019
So that sweeper failures don't stop other sweepers/tests.

[megan07]

I've added -sweep-allow-failures to all the Google projects in TC, and tests still ran last night (which was my test). I'll close this now.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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