profiler: try all us-west1 zones for integration tests
profiler: try all us-west1 zones for integration tests

Previously there were issues when trying to create instances in a
particular zone that was resource constrained. Instead of just
trying one zone, let's try all zones in the region.

Fixes: #1876

Change-Id: I18187c16ea2af5fd93c4a6e2a6d22f8a593a3905
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/53690
Reviewed-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Noah Dietz <892d271bd3cbb39857a7b053afeb6c28a7075b07@google.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go