LU-8500 ldlm: fix export reference problem

LU-8500 ldlm: fix export reference problem

1, in client_import_del_conn, the export returned from
   class_conn2export is not released after using it.

2, in ptlrpc_connect_interpret, the export is not released
   if the connect_flags isn't compatible.

Change-Id: Ie7ef9cb0de2fa1aba71d3981ce47ae87c75e82d8
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: http://review.whamcloud.com/22031
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>