vdsm: bridge: attempt to rollback if bridge creation failed

Currently vdsm-bootstrap, host-deploy, vdsm-reg do not rollback network
configuration if addNetwork fails.

The sequence should be:
- addNetwork
- vdsm-restore-net-config -> rollback
- vdsm-store-net-config -> commit

Supporting non-node setup is not important to 3.3 as only legacy nodes
still use the ovirt-host-deploy bridge plugin.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=979570
Change-Id: Id9e6b0d076f3a16f036e149258454da395569797
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>