Added /strategies endpoint in Watcher API

In this changeset, I added the /strategies endpoint to the Watcher
API service.
This also includes the related Tempest tests.

Partially Implements: blueprint get-goal-from-strategy

Change-Id: I1b70836e0df2082ab0016ecc207e89fdcb0fc8b9

watcher/decision_engine/strategy/context/default.py

@@ -26,6 +26,7 @@ LOG = log.getLogger(__name__)
 
 
 class DefaultStrategyContext(base.BaseStrategyContext):
+
     def __init__(self):
         super(DefaultStrategyContext, self).__init__()
         LOG.debug("Initializing Strategy Context")