multipath: add '-t' option to dump internal hwtable

multipath: add '-t' option to dump internal hwtable

This patch adds an option '-t' to dump the internal hardware table.
Quite handy if you want to know the default settings.
In doing so it also fixes the keyword allocation; currently the
keywords are only initialised if a configuration file is used.

Signed-off-by: Hannes Reinecke <hare@suse.de>