engine: Geo-rep monitoring

Monitoring details of geo rep sessions - detects
new sessions and updates the database
Consolidates the session status based on individual
node status
Removes sessions from database if deleted from CLI
Corrected errors with wrong session id while retrieving
from VDS and status while saving to DB.

Change-Id: I3304addda17cf49eee93f311e043b0e15212cd91
Bug-Url: https://bugzilla.redhat.com/1138116
Signed-off-by: Sahina Bose <sabose@redhat.com>