Updates for stable branch creation

Set default branch for git review/gerrit.

Switch amulet tests to stable.

Switch to using stable charm-helpers branch.

Change-Id: I7ca47c8ff68a8a8c8bcbd6c3ad523ddc7d852409

.gitreview

@@ -2,3 +2,5 @@
 host=review.opendev.org
 port=29418
 project=openstack/charm-barbican.git
+
+defaultbranch=stable/19.10

src/tests/basic_deployment.py

@@ -19,7 +19,7 @@ u = OpenStackAmuletUtils(DEBUG)
 class BarbicanBasicDeployment(OpenStackAmuletDeployment):
     """Amulet tests on a basic Barbican deployment."""
 
-    def __init__(self, series, openstack=None, source=None, stable=False):
+    def __init__(self, series, openstack=None, source=None, stable=True):
         """Deploy the entire test environment.
         """
         super(BarbicanBasicDeployment, self).__init__(

src/wheelhouse.txt

@@ -1,3 +1,5 @@
 
 jinja2
 psutil
+
+git+https://opendev.org/openstack/charms.openstack.git@stable/19.10#egg=charms.openstack