afs: Fix server rotation's handling of fileserver probe failure

afs: Fix server rotation's handling of fileserver probe failure

BugLink: http://bugs.launchpad.net/bugs/1794889
[ Upstream commit ec5a3b4b507efca903d848518dcf2ebf7b04b466 ]

The server rotation algorithm just gives up if it fails to probe a
fileserver.  Fix this by rotating to the next fileserver instead.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>