When ntsync_obj_get_fd() fails, we free the ntsync object but forget to drop the
"file" member.
This was fixed for semaphores in 0e7d523b5f7a23b1dc6ceceb04e31a60e9e3321d, but
that commit did not fix the similar leak for events and mutexes, since they were
part of patches not yet in the mainline kernel. Fix those cases.