afs: Handle the VIO and UAEIO aborts explicitly

When processing the result of a call, handle the VIO and UAEIO abort
specifically rather than leaving it to a default case.  Rather than
erroring out unconditionally, see if there's another server if the volume
has more than one server available, otherwise return -EREMOTEIO.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org