b=17617 (in fact this is part of 17310 for HEAD)

- fixes manual_umount_client() in conf_sanity.sh to handle --force correctly as it is used by number of tests (this part should be missed in tests porting);

- add assert before decref mgc refcounter;
- fixed possible leaked niduuid in case of error;
- kill @rc in server_put_super() as it is not used;
- use OBD_FAIL_CHECK_ORSET in ptlrpc_check_set() to avoid assert;
- enable test_45 as it is working now.