staging/lustre/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.

Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: http://review.whamcloud.com/22031
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8500


Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>