Do not build iso for ussuri ipa

Since ipa-builder is branchless its code is used directly from master to
test ipa in stable releases.
The iso has been fixed only recently, and since we need to use
ipa-builder version 2.2.0 in stable/ussuri to test, build and publish
the ipa ramdisk, we can't also build an iso in CI or the build job will
break.
As a result we do not buildi an iso for ussuri ironic-python-agent.

Change-Id: I4801e87f5b3c37f113bfc9578c8e2aaa4d4f32f0

roles/ipa-build-tinyipa-image/tasks/main.yaml

@@ -1,11 +1,20 @@
 - name: Build a TinyIPA image
-  command: make all
+  command: make
   args:
     chdir: '{{ tinyipa_dir }}'
   environment:
     BRANCH_PATH: '{{ ipa_branch_path }}'
     IPA_SOURCE_DIR: '{{ ansible_user_dir }}/src/opendev.org/openstack/ironic-python-agent'
 
+- name: Build a TinyIPA iso
+  command: make iso
+  args:
+    chdir: '{{ tinyipa_dir }}'
+  environment:
+    BRANCH_PATH: '{{ ipa_branch_path }}'
+    IPA_SOURCE_DIR: '{{ ansible_user_dir }}/src/opendev.org/openstack/ironic-python-agent'
+  when: "'ussuri' not in ipa_branch_path"
+
 - name: Move resulting files
   shell: |
     mv tinyipa*.tar.gz* "{{ ipa_tar_dir }}"