Fix bug 1263

Update database endpoints when a new VCA_HOST_IP is provided

Before, we were not considering the that the VCA_HOST_IP could be
updated, in that case, the old ips stored in the database should be
replace by the new one. Of course, this won't do any model migration
from the previous VCA to the new one. It will only start pointing to
the new VCA provided.

Change-Id: I5e259f773f90e4f440d87c4b6342cd82425c0e0c
Signed-off-by: David Garcia <david.garcia@canonical.com>