Linux: Refine openafs-client.service dependencies

Make sure that openafs-client is started after the network is online,
and before services that need remote-fs at startup.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/11441
Reviewed-by: Chaskiel Grundman <cg2v@andrew.cmu.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit cadaea4f86427c4dc74f56fc66707e8cfb0166cb)

Change-Id: I42aea5dff364e1005808b6ae926f6cf1bf2e0d61
Reviewed-on: http://gerrit.openafs.org/11534
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>