JCBC-312: When vbucket master is -1, trigger reconfigure.

This changeset makes sure that when no active master is found,
reconfiguration is properly triggered.

Change-Id: I5f4f2b9aac9db1b536cba596e8ed062453b7a263
Reviewed-on: http://review.couchbase.org/26636
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Deepti Dawar <deepti.dawar@globallogic.com>