Make ironic's service check flexible

We currently assume we are deploying ironic with the rest of
a cloud and assert that glance/neutron/nova are enabled. This
makes it a bit more flexible and allows deploying with only
the minimum required services if desired, and asserts the others
are enabled when we intend on testing nova+ironic integration.

This is required for in-tree python-ironicclient functional tests,
which we aim to run against a minimal devstack deployment.

Change-Id: I99001d151161fa225b97c3ba6b167a61aa9b59fe

lib/ironic

@@ -180,7 +180,11 @@ function is_deployed_with_ipa_ramdisk {
 # install_ironic() - Collect source and prepare
 function install_ironic {
     # make sure all needed service were enabled
-    for srv in nova glance key; do
+    local req_services="mysql rabbit key"
+    if [[ "$VIRT_DRIVER" == "ironic" ]]; then
+        req_services+=" nova glance neutron"
+    fi
+    for srv in $req_services; do
         if ! is_service_enabled "$srv"; then
             die $LINENO "$srv should be enabled for Ironic."
         fi

lib/nova_plugins/hypervisor-ironic

@@ -54,9 +54,7 @@ function configure_nova_hypervisor {
 
 # install_nova_hypervisor() - Install external components
 function install_nova_hypervisor {
-    if ! is_service_enabled neutron; then
-        die $LINENO "Neutron should be enabled for usage of the Ironic Nova driver."
-    elif is_ironic_hardware; then
+    if is_ironic_hardware; then
         return
     fi
     install_libvirt