datastore: reduce initial retry timeout from 1s to 100ms
datastore: reduce initial retry timeout from 1s to 100ms

Change-Id: I05f7ed58d996b7fbac52fc31d3dc89b36eb69525
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/43090
Reviewed-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Emmanuel Odeke <277f8eaa8c7dfbc55c17bf5e30561c1a9c45c569@gmail.com>

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