bigtable: fix retry test
bigtable: fix retry test

Add WithBlock to the grpc.Dial call, remove from NewClient calls.

Also, test for error before defer.

Change-Id: I6febdac6fd6f5b938477dc4e94e9cae9ba31a2e3
Reviewed-on: https://code-review.googlesource.com/18090
Reviewed-by: Gary Elliott <d49662846a332c09d32ce16a761e8169b9defdba@google.com>
Reviewed-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

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