kclient: drop any unwanted caps when unlinking a file
kclient: drop any unwanted caps when unlinking a file

Since we can't reopen an unlinked file, there's no reason to hold on to
them.  And the MDS will often want to lock to update max_size, which could
mean spurious revocations.  At the very least, make sure we drop the LINK
caps.

Do the same for the rename target, if it exists.

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph