exabgp: peer groups in Quagga seems to be buggy with rsclient and IPv6

Quagga is advertising IPv4 AFI while it should advertise IPv6
AFI. Since peer can advertise IPv6 AFI only, there is a capability
mismatch in MP-ext.
exabgp: use --no_kernel for Quagga bgpd instead of views

As suggested by Nick Hilliard, don't use views + RS client since it is
likely to be buggy.