nova: Ensure each compute uses a unique iSCSI initiator

The current initiator name embedded in our CI images is not unique at
present and can often cause failures during live migrations with
attached volumes. This change ensures the name is unique by running
iscsi-iname again and overwriting the existing name.

We could potentially do this during the image build process itself but
given that devstack systems are not supposed to be multi-purpose this
should be safe to do during the devstack run.

NOTE(lyarwood): Conflict due to
If2f74f146a166b9721540aaf3f1f9fce3030525c not being present on
stable/wallaby.

Conflicts:
    lib/nova

Closes-Bug: #1945983
Change-Id: I9ed26a17858df96c04be9ae52bf2e33e023869a5
(cherry picked from commit 714826d1a2)
(cherry picked from commit ee629cc775)

lib/nova

@@ -304,6 +304,9 @@ function configure_nova {
             sudo dnf update -y
         fi
 
+        # Ensure each compute host uses a unique iSCSI initiator
+        echo InitiatorName=$(iscsi-iname) | sudo tee /etc/iscsi/initiatorname.iscsi
+
         if [[ ${ISCSID_DEBUG} == "True" ]]; then
             # Install an override that starts iscsid with debugging
             # enabled.