afsd: Do not check for /afs if -nomount

afsd: Do not check for /afs if -nomount

If -nomount was passed, we don't try to mount /afs. So, there is no
reason to require its existence.

Reviewed-on: http://gerrit.openafs.org/3822
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit c15468e2605446fa89e351131ba429a360d823f8)

Change-Id: I58f4a600fe976703412b76d7aeba1e316e08d05b
Reviewed-on: http://gerrit.openafs.org/3877
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>