Do not wait for grace period for not-my-vbucket retries

This reduces the wait time for any not-my-vbucket retry. This is in light of the other modifications made to the library to allow it to properly utilize the "found incorrect master" ff-map lookup pattern, in which the command is not retried on the same server again.

In this case, the library makes an implicit assumption that there will always be one server which will be the correct server (and it would be either online of offline), and will not give us a not-my-vbucket.