cmd: Split up dispatch function

cmd: Split up dispatch function

Split up the command line parsing behaviour out of the cmd_Dispatch
function, and into a function of its own - cmd_Parse. This lets servers
which only have a single "syntax" installed just parse, without needing
to go through a dispatch function, and all of the control flow
complexity that requires.

Change-Id: Ic4325bf933ee5b28cb80db36ef9b2b5fb6763f41
Reviewed-on: http://gerrit.openafs.org/4541
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>