ptserver: Use libcmd for command line parsing

ptserver: Use libcmd for command line parsing

Modify the ptserver so that it uses the libcmd library to parse its
command line, rather than rolling its own command line parsing.

Change-Id: I84bac2cd70bbaf85004fce2f23d9237215544edd
Reviewed-on: http://gerrit.openafs.org/5073
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>