pagsh: do not call set[ug]id()

pagsh: do not call set[ug]id()

Supposedly calling setuid(getuid()) and setgid(getgid()) would
help pick up a new group list on some systems, in the depths
of history.  In the absence of reason to believe this is still
the case, drop the calls to avoid scary warnings about unchecked
return values.

Change-Id: I39e87a27fb52f5a6868b867c9325d4a5fa93ef58
Reviewed-on: http://gerrit.openafs.org/11759
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>