Provide more detailed errors on bucket creation failures.
Provide more detailed errors on bucket creation failures.

In particular, when a bucket exists, the error reports the state the
bucket is in.

Change-Id: I4eb12df9089bddc23d750757b51c8a9d6b4bea20
Reviewed-on: http://review.northscale.com/2924
Reviewed-by: Sean Lynch <9c3328a4a1f4f8f5c18b2d5b9057163c49b93ff3@literati.org>
Tested-by: Sean Lynch <9c3328a4a1f4f8f5c18b2d5b9057163c49b93ff3@literati.org>

membase/bucket_engine,couchbase/bucket_engine,membase/bucket_engine,couchbase/bucket_engine,couchbase/bucket_engine,membase/bucket_engine,couchbase/bucket_engine,membase/bucket_engine