Add --controller, --lxd-cloud and --lxd-credentials in osm installer using charms

- LXD Cloud: Takes a YAML file as a parameter with the LXD Cloud information
- LXD Credentials: Takes a YAML file as a parameter with the LXD Credentials information

Change-Id: I0f09e15eb00c0d64d91154d6d55c1ec3d12ee31a
Signed-off-by: David Garcia <david.garcia@canonical.com>