Stop nova services before doing a db sync; start them after the sync

Sometimes, running openstack_nova.sh results in several nova-conductor
services being created.
To avoid that, one solution is to stop the nova services before doing a
db sync, and to start them after the sync.
See
https://bugs.launchpad.net/charms/+source/nova-cloud-controller/+bug/1347245

Signed-off-by: Flavien Quesnel <flavien.quesnel@irt-systemx.fr>
Modify the way to grab the rig's ip address

The regular expression does not always catch the rig's IP address.
One solution is to directly ask the user for the IP.

Signed-off-by: Flavien Quesnel <flavien.quesnel@irt-systemx.fr>