add "registry" flag to "tools/build.py"

With registry flag,
build image using `tools/build.py --registry 172.22.2.81:4000`
the image name looks like `172.22.2.81:4000/kollaglue/data`
When user use kolla-ansible,
user set `docker_registry` to `172.22.2.81:4000` in `/etc/kolla/globals.yml`.

Build image using `tools/build.py -n abcd`
the image name looks like `abcd/data`
When user use kolla-ansible,
user set `docker_namespace:` to `abcd` in `/etc/kolla/globals.yml`.

build image using `tools/build.py -n abcd --registry 172.22.2.81:4000`
the image name looks like `abcd/data`
When user use kolla-ansible,
user set `docker_namespace:` to `abcd` in `/etc/kolla/globals.yml`.
user set `docker_registry` to `172.22.2.81:4000` in `/etc/kolla/globals.yml`.

With the feature, it will reduce user confusing and mistaking.

Change-Id: I18ac7a3ccec032888e35f5e9a79fc190760cc8a0
Closes-Bug: #1505056
(cherry picked from commit 52b7253811)

doc/deploy-all-in-one-node.rst

@@ -37,7 +37,7 @@ The guide assumes that you have build images using the following command.
 
 ::
 
-    tools/build.py -n 172.22.2.81:4000/kollaglue --base ubuntu --type source --push
+    tools/build.py --registry 172.22.2.81:4000 --base ubuntu --type source --push
 
 The IP, "172.22.2.81", is the host running private docker registry.
 To deploy a private docker registry,

etc/kolla/kolla-build.conf

@@ -42,6 +42,8 @@
 # Path to custome file to be addded at end of Dockerfiles for final images
 #include_footer = /path/to/footer_file
 
+# The registry host. The default registry host is Docker Hub.
+#registry = None
 
 # Provide location of sources for source install builds.
 # Example:

kolla/cmd/build.py

@@ -225,7 +225,8 @@ def merge_args_and_config(settings_from_config_file):
         "keep": False,
         "push": False,
         "threads": 8,
-        "retries": 3
+        "retries": 3,
+        "registry": None
     }
     defaults.update(settings_from_config_file.items('kolla-build'))
     parser.set_defaults(**defaults)
@@ -282,6 +283,9 @@ def merge_args_and_config(settings_from_config_file):
                         help=('Path to custom file to be added at '
                               'end of Dockerfiles for final images'),
                         type=str)
+    parser.add_argument('--registry',
+                        help=("the docker registry host"),
+                        type=str)
     return vars(parser.parse_args())
 
 
@@ -291,7 +295,11 @@ class KollaWorker(object):
         self.base_dir = os.path.abspath(find_base_dir())
         LOG.debug("Kolla base directory: " + self.base_dir)
         self.images_dir = os.path.join(self.base_dir, 'docker')
-        self.namespace = config['namespace']
+        self.registry = config['registry']
+        if self.registry:
+            self.namespace = self.registry + '/' + config['namespace']
+        else:
+            self.namespace = config['namespace']
         self.base = config['base']
         self.base_tag = config['base_tag']
         self.install_type = config['install_type']