libuafs: Allow -mountdir to override uafs_Setup

libuafs: Allow -mountdir to override uafs_Setup

For some reason, uafs_Setup accepts a parameter specifying the AFS mount
point, and we effectively ignore any -mountdir option specified in the
string arguments. Allow -mountdir to override the mount point specified
in uafs_Setup, by changing afs_mountDir &co during afsd_mount_afs().

Reviewed-on: http://gerrit.openafs.org/3897
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 1f1545dfb708b6f70065da58b44676b8eafef772)

Change-Id: Id57dea754bb8f2e45b3128afadb52aeea97c4f13
Reviewed-on: http://gerrit.openafs.org/4084
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>