s4:rpc_server: make sure we don't terminate a connection with pending requests (bug...

s4:rpc_server: make sure we don't terminate a connection with pending requests (bug #9820)

Sadly we may have nested event loops, which won't work correctly with
broken connections, that's why we have to do this...

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Jul 10 08:47:38 CEST 2013 on sn-devel-104
(cherry picked from commit e6a58d370403e818bc2cfb8389751b78adcc14fd)