Refactor Tower HA Instance logic and models

* Gut the HA middleware
* Purge concept of primary and secondary.
* UUID is not the primary host identifier, now it's based mostly on the
  username.  Some work probably still left to do to make sure this is
  legit.  Also removed unique constraint from the uuid field.  This
  might become the cluster ident now... or it may just deprecate
* No more secondary -> primary redirection
* Initial revision of /api/v1/ping
* Revise and gut tower-manage register_instance
* Rename awx/main/socket.py to awx/main/socket_queue.py to prevent
  conflict with the "socket" module from python base
* Revist/gut the Instance manager... not sure if this manager is really
  needed anymore

awx/main/middleware.py

@@ -71,41 +71,6 @@ class ActivityStreamMiddleware(threading.local):
                 if instance.id not in self.instance_ids:
                     self.instance_ids.append(instance.id)
 
-
-class HAMiddleware(object):
-    """A middleware class that checks to see whether the request is being
-    served on a secondary instance, and redirects the request back to the
-    primary instance if so.
-    """
-    def process_request(self, request):
-        """Process the request, and redirect if this is a request on a
-        secondary node.
-        """
-        # Is this the primary node? If so, we can just return None and be done;
-        # we just want normal behavior in this case.
-        if Instance.objects.my_role() == 'primary':
-            return None
-
-        # Always allow the /ping/ endpoint.
-        if request.path.startswith('/api/v1/ping'):
-            return None
-
-        # Get the primary instance.
-        primary = Instance.objects.primary()
-
-        # If this is a request to /, then we return a special landing page that
-        # informs the user that they are on the secondary instance and will
-        # be redirected.
-        if request.path == '/':
-            return TemplateResponse(request, 'ha/redirect.html', {
-                'primary': primary,
-                'redirect_seconds': 30,
-                'version': version,
-            })
-
-        # Redirect to the base page of the primary instance.
-        return HttpResponseRedirect('http://%s%s' % (primary.hostname, request.path))
-
 class AuthTokenTimeoutMiddleware(object):
     """Presume that when the user includes the auth header, they go through the
     authentication mechanism. Further, that mechanism is presumed to extend