Update DEVSTACK_GATE_* vars for ironic-standalone
Update the following devstack-gate variables to pick correct values
DEVSTACK_GATE_VIRT_DRIVER=ironic
DEVSTACK_GATE_IRONIC_DRIVER=agent_ipmitool
export DEVSTACK_GATE_IRONIC=1
export DEVSTACK_GATE_NEUTRON=1
export DEVSTACK_GATE_IRONIC_BUILD_RAMDISK=0
+ export DEVSTACK_GATE_VIRT_DRIVER=ironic
+ export DEVSTACK_GATE_IRONIC_DRIVER=agent_ipmitool
export OVERRIDE_ENABLED_SERVICES="g-api,g-reg,q-agt,q-dhcp,q-l3,q-svc,key,mysql,rabbit,ir-api,ir-cond,s-account,s-container,s-object,s-proxy,tempest"
export BRANCH_OVERRIDE={branch-override}
