Set kolla tag in base config

This fixes an issue when building local images. The symptoms were:

```
Traceback (most recent call last):
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/kolla/image/build.py", line 565, in builder
    buildargs=buildargs):
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/api/build.py", line 269, in build
    timeout=timeout,
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/utils/decorators.py", line 46, in inner
    return f(self, *args, **kwargs)
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/api/client.py", line 233, in _post
    return self.post(url, **self._set_request_timeout(kwargs))
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 577, in post
    return self.request('POST', url, data=data, json=json, **kwargs)
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 529, in request
    resp = self.send(prep, **send_kwargs)
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 645, in send
    r = adapter.send(request, **kwargs)
  File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/adapters.py", line 501, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', ConnectionResetError(104, 'Connection reset by peer'))
```

and the following error in `journalctl -u docker`:

```
level=error msg="Handler for POST /v1.41/build returned error: invalid reference format"
```

The issue was that it was trying to use a jinja interpreted string as
the image tag.

Author: jovial

etc/kayobe/environments/ci-builder/kolla.yml

@@ -100,7 +100,7 @@ kolla_openstack_release: "{% raw %}{{ kayobe_image_tags['openstack'][kolla_base_
 
 # Docker tag applied to built container images. Default is
 # {{ kolla_openstack_release }}.
-#kolla_tag:
+kolla_tag: "{{ openstack_release }}-{{ ansible_facts.date_time.iso8601_basic_short }}"
 
 # Dict mapping names of sources to their definitions for
 # kolla_install_type=source. See kolla.common.config for details.

etc/kayobe/kolla.yml

@@ -0,0 +1,26 @@
+---
+fixes:
+  - |
+    Fixes an issue with local image builds where kolla_tag had not been set.
+    The error had the signature:
+
+    .. code-block:
+
+      Traceback (most recent call last):
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/kolla/image/build.py", line 565, in builder
+          buildargs=buildargs):
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/api/build.py", line 269, in build
+          timeout=timeout,
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/utils/decorators.py", line 46, in inner
+          return f(self, *args, **kwargs)
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/docker/api/client.py", line 233, in _post
+          return self.post(url, **self._set_request_timeout(kwargs))
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 577, in post
+          return self.request('POST', url, data=data, json=json, **kwargs)
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 529, in request
+          resp = self.send(prep, **send_kwargs)
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/sessions.py", line 645, in send
+          r = adapter.send(request, **kwargs)
+        File "/opt/kayobe/venvs/kolla/lib/python3.6/site-packages/requests/adapters.py", line 501, in send
+          raise ConnectionError(err, request=request)
+      requests.exceptions.ConnectionError: ('Connection aborted.', ConnectionResetError(104, 'Connection reset by peer'))