Flap all XMPP connections if the ASN changes.

The ASN is embedded in a few extended communities such as OriginVn and
SecurityGroup.  If the ASN changes, we need to update all XMPP learnt
routes to have these extended communities based on the new ASN.  Since
an ASN change is expeceted to be a very infrequent event, we choose to
handle it by flapping all the connections instead of updating all the
routes.

Change-Id: I333decdeaaf70f5f58b84bdc85fe447bb82c8737
BgpConfig code is too aggressive in treating nodes as deleted.

BgpPeers sometimes do not come up when repeatedly doing delete
and add in the bgp_stress_test via [DELETE|ADD]_BGP_PEER events.

Root cause is that the config code does not look at IFMap nodes
that have no neighbors in the graph i.e. it considers them to
be deleted.  This can cause a problem if a bgp-router node is
added and processed before parent link to the routing-instance
has been processed.  In this case, the BgpProtocolConfig that
corresponds to the bgp-router is not created.

Fix is to not consider IFMap nodes without neighbors as deleted.

Also fix minor issue wherein the creation of a BgpPeeringConfig
would get logged as a create and an update.

Change-Id: I44c1d6de17a7a495cc18a5ddd20a05dde8b8b3fb