BGP: Fix BGP unnumbered peerings across VRFs

BGP: Fix BGP unnumbered peerings across VRFs

Upon receipt of incoming connection, a peer structure (doppelganger) is
created internally and the connection processed for it. The problem is
that in the case of BGP unnumbered, the sockunion structure within BGP was
being updated (in peer_create()) prior to the peer's flags being updated,
so it didn't take into account the 'v6only' configuration. This results
in subsequent problems when bgp_bind() is done - the socket ends up being
bound to the BGP instance instead of the interface.

In the case of an incoming connection, we should just use the addresses
on which the connection was setup/accepted, there is no need to attempt to
derive it again. Further, there is no need to attempt to update addresses
at the time of peer_create() since that is done when the connection is
attempted in bgp_start().

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>
Reviewed-by: Don Slice <dslice@cumulusnetworks.com>
Ticket: CM-10028
Reviewed By: CCR-4373
Testing Done: Manual, bgpsmoke