vos: Default to server confdir for -localauth

vos: Default to server confdir for -localauth

For -localauth, we traditionally default to using the server
configuration directory, since that's usually the dir that has the
KeyFile in it. Keep doing that with the new ubik client interface.

Change-Id: I0f7e1ed180874f52c2b91b1ea3f74e763c26cd0c
Reviewed-on: http://gerrit.openafs.org/7324
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Tom Keiser <tkeiser@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementix.org>