Add DCERPC flag to call unbind hooks without destroying the connection itself upon termination of a connection with outstanding pending calls.

Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jelmer Vernooij <jelmer@samba.org>

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Apr 14 20:39:34 CEST 2015 on sn-devel-104
