Eventscript functions - optimise is_ctdb_managed_service().

Eventscript functions - optimise is_ctdb_managed_service().

This function generates a lot of trace when running under "set -x".
This is due to the backward compatibility code.

This adds 3 optimisations:

1. Before invoking the backward compatiblity code,
   is_ctdb_managed_service() returns early if the service is listed in
   $CTDB_MANAGED_SERVICES.

2. ctdb_compat_managed_service() actually now updates
   $CTDB_MANAGED_SERVICES instead of temporary variable $t.

   This means that a subsequent call to is_ctdb_managed_service() will
   short circuit due to optimisation (1).

3. ctdb_compat_managed_service() only adds a service to
   $CTDB_MANAGED_SERVICES if it is the service being checked by
   is_ctdb_managed_service().

   This stops irrelevant services being added to
   $CTDB_MANAGED_SERVICES multiple times by multiple calls to
   is_ctdb_managed_service().

Signed-off-by: Martin Schwenke <martin@meltin.net>