setup-multipath: save the 'root_mpath' variable

We need to save the root_mpath variable, otherwise it won't be
seen during booting.

References: bnc#854243

Signed-off-by: Hannes Reinecke <hare@suse.de>
- Update Changelog.
Blacklist HP Virtual devices

References: bnc#862250

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