afs: Connect up the CB.ProbeUuid

[ Upstream commit f4b3526d83c40dd8bf5948b9d7a1b2c340f0dcc8 ]

The handler for the CB.ProbeUuid operation in the cache manager is
implemented, but isn't listed in the switch-statement of operation
selection, so won't be used.  Fix this by adding it.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>