devstack: When Python 3 enabled, use Python 3

In order to have Ironic installed using Python 3 when running under a
Python 3 test job, we need to enable it as a Python 3 package.

The Python 3 job still doesn't pass. But this is needed as part of the
work.

Change-Id: I6a766bbb4250d76d458db8783631e4bd834859f3

devstack/plugin.sh

@@ -7,6 +7,11 @@
 echo_summary "ironic devstack plugin.sh called: $1/$2"
 source $DEST/ironic/devstack/lib/ironic
 
+# These packages should be tested under python 3, when the job enables Python 3
+# TODO(jlvillal) Add additional dependencies when they should support Python 3.
+#     Add: pyghmi and virtualbmc when they are ready
+enable_python3_package ironic ironic-lib ironic-python-agent python-ironicclient
+
 if is_service_enabled ir-api ir-cond; then
     if [[ "$1" == "stack" ]]; then
         if [[ "$2" == "install" ]]; then