afsd.fuse: Force internal mount dir to /afs

afsd.fuse: Force internal mount dir to /afs

Commit 1f1545dfb708b6f70065da58b44676b8eafef772 made it so the
argument given to -mountdir sets the internal mount directory.
However, afsd.fuse assumes that the mount dir is always /afs
internally. So, use the uafs_setMountDir function to reset the
internal mount dir to "/afs", so afsd.fuse can work with non-/afs
mountpoints.

Reviewed-on: http://gerrit.openafs.org/3979
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 18b24156f1dc0f727260724023eed583b460218b)

Change-Id: Icc856771c82332ee6dcd25692da80c28d2effe99
Reviewed-on: http://gerrit.openafs.org/4086
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>