During the session establishment phase, if a peer doesn't advertise ipv4-unicast, controller automatically adds ipv4-unicast as supported family for the session to support classic BGP sessions. Currently, we are adding Ipv4 family in the BGPPeer but not updating AdjRibInWriter which causes the BGP session to not recover from session flap.

Patch fixes this issue by adding ipv4 support before updating AdjRibInWriter.