autoinstall: add labs-hosts1-b-eqiad subnet

While we do have a subnets/labs-hosts1-b-eqiad.cfg configuration file,
it was unreferenced from the subnet detection in netboot.cfg. Fix this.

Change-Id: Iae327c058e6f417739480d0d44291df36f57a261
autonstall: switch eqiad subnets to use eqiad's NS

It only matters for the install phase, but let's not make installs
dependent on the other datacenter as much. Switch the NS set for eqiad
subnets to 208.80.154.239 & 208.80.152.131 (eqiad/pmtpa) instead of
208.80.152.131 208.80.152.132 (both pmtpa).

Change-Id: Ifd8292e78ea679553d3cc3836c9f21482e8d5f97