ptserver: Rename ubik.c as ptubik.c

Coverity gets confused between ubik/ubik.c and ptserver/ubik.c,
and produces a load of false positives. Rename the ptserver ubik
shim (which is only used by pt_util) in order to reduce this
confusion.

Change-Id: Ida606fccebcb4edfed706405424ff3ee4858020f
Reviewed-on: http://gerrit.openafs.org/9273
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>