mds: allow Objecter to dispatch its own messages

Signed-off-by: Sage Weil <sage@redhat.com>
librados/RadosClient: remove unused get_pool_name()

Signed-off-by: Sage Weil <sage@redhat.com>
librados: wait for map on create_ioctx failure

Ensure we have a map so we don't simply complain that a pool doesn't
exists.  Only take the lock and wait if we fail to lookup the pool,
though, so we avoid contending the lock in the general case.

Signed-off-by: Sage Weil <sage@redhat.com>