bgpd: use bgp->name_pretty in debugs and add vrf to some output

bgpd: use bgp->name_pretty in debugs and add vrf to some output

Recently had a case where I was attempting to debug a nexthop tracking
issue across multiple bgp vrf's and since the setup vrf's in it with
overlapping address ranges, it became real fun real fast to track
vrf data associated.  Add a bit of code to allow us to figure out
what vrf we are in when we print out debug messages.

Look through the rest of the code and find debugs where we are
not using bgp->name_pretty and switch it over.

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