bgpd: Try to notice when configuration changes during startup

bgpd: Try to notice when configuration changes during startup

During peer startup there exists the possibility that both
locally and remote peers try to start communication at the
same time.  In addition it is possible for local configuration
to change at the same time this is going on.  When this happens
try to notice that the remote peer may be in opensent or openconfirm
and if so we need to restart the connection from both sides.

Additionally try to write a bit of extra code in peer_xfer_conn
to notice when this happens and to emit a error message to
the end user about this happening so that it can be cleaned up.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>