vlserver: Add options for config, log and db

vlserver: Add options for config, log and db

Make it possible to set the location of the vlserver's configuration
directory, database file, and the file that it logs to, from the
command line. This makes it possible to bring up a vlserver without
requiring an installation on the system for testing purposes.

Change-Id: I0a3fcc4fd10274588c1530f8b4f3e9782084c58c
Reviewed-on: http://gerrit.openafs.org/4440
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>