ctdb-client: Only get capabilities from active nodes

ctdb-client: Only get capabilities from active nodes

This is used by the recovery daemon to validate the current recovery
master.  Don't risk being unable to elect a new master if the current
master is inactive but unresponsive.

Note that this client call is currently not used by any other callers.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Sun Dec 13 03:17:10 CET 2015 on sn-devel-104