Allow coordinator non-string options and use them

To allow the zake driver to use a pre-existing storage
backend (for example, shared with a taskflow test that
also uses zake) we need a way to provide non-query-string
options and to get those options to the zake driver for
usage.

This approach allows the `get_coordinator` function
to take **kwargs and have those take precedence over
the options found with the same name in the urls query
string (and merge those together to form the coordinators
option dictionary that exists already).

Change-Id: Ibc745927eccac050992227410cca393d956f8c44

tooz/coordination.py

@@ -340,21 +340,33 @@ class CoordAsyncResult(object):
         """Returns True if the task is done, False otherwise."""
 
 
-def get_coordinator(backend_url, member_id):
+def get_coordinator(backend_url, member_id, **kwargs):
     """Initialize and load the backend.
 
     :param backend_url: the backend URL to use
     :type backend: str
     :param member_id: the id of the member
     :type member_id: str
+    :param kwargs: additional coordinator options (these take precedence over
+                   options of the **same** name found in the ``backend_url``
+                   arguments query string)
     """
     parsed_url = netutils.urlsplit(backend_url)
     parsed_qs = six.moves.urllib.parse.parse_qs(parsed_url.query)
+    if kwargs:
+        options = {}
+        for (k, v) in six.iteritems(kwargs):
+            options[k] = [v]
+        for (k, v) in six.iteritems(parsed_qs):
+            if k not in options:
+                options[k] = v
+    else:
+        options = parsed_qs
     return driver.DriverManager(
         namespace=TOOZ_BACKENDS_NAMESPACE,
         name=parsed_url.scheme,
         invoke_on_load=True,
-        invoke_args=(member_id, parsed_url, parsed_qs)).driver
+        invoke_args=(member_id, parsed_url, options)).driver
 
 
 class ToozError(Exception):

tooz/drivers/zake.py

@@ -35,4 +35,8 @@ class ZakeDriver(zookeeper.KazooDriver):
 
     @classmethod
     def _make_client(cls, parsed_url, options):
-        return fake_client.FakeClient(storage=cls.fake_storage)
+        if 'storage' in options:
+            storage = options['storage'][-1]
+        else:
+            storage = cls.fake_storage
+        return fake_client.FakeClient(storage=storage)