Remove q-dhcp from gate job tests
Remove q-dhcp from gate job tests

devstackgaterc is used for all dragonflow gate jobs to
determine which services are enabled in the gate.
remove q-dhcp as we want to test Dragonflow DHCP impl.

Change-Id: I732548ca8fd147b66031799245eafd506ea5c753

openstack/dragonflow,FrankDuan/df_code,openstack/dragonflow,FrankDuan/df_code,openstack/dragonflow,FrankDuan/df_code