Add Designate BIND9 DSVM Job

Refactor the gate-designate-devstack-dsvm job to be a reusable
job template, turning it into gate-designate-dsvm-powerdns, and
create a second instance for the BIND9 designate driver.

Change-Id: I7c5321e82caf8d54cf74095cea18dd1ea5b5bac5
Merge "Add Designate BIND9 DSVM Job"