afs: put back conn if not using in checkserver loop

afs: put back conn if not using in checkserver loop

we get a conn, check it for eligibility, and if not,
just abandon it. "oops"

Change-Id: Ie3841c19b05a87fb225c3e8124cd485cba3c3648
Reviewed-on: http://gerrit.openafs.org/6516
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Derrick Brashear <shadow@dementix.org>