Tests dir no longer need copy of charmhelpers

Charmhelpers is now installed via pip for unit tests so stop
'Make sync' from pulling it down.

Change-Id: Ic1a646b0232980f169a03894bda52451a82a5eec

Makefile

@@ -19,7 +19,6 @@ bin/charm_helpers_sync.py:
 
 sync: bin/charm_helpers_sync.py
 	@$(PYTHON) bin/charm_helpers_sync.py -c charm-helpers-hooks.yaml
-	@$(PYTHON) bin/charm_helpers_sync.py -c charm-helpers-tests.yaml
 
 publish: lint test
 	bzr push lp:charms/neutron-gateway

charm-helpers-tests.yaml

@@ -1,13 +0,0 @@
-repo: https://github.com/juju/charm-helpers
-destination: tests/charmhelpers
-include:
-    - fetch
-    - core
-    - contrib.amulet
-    - contrib.openstack.amulet
-    - contrib.openstack.utils
-    - contrib.openstack.exceptions
-    - contrib.network.ip
-    - contrib.storage|inc=*
-    - contrib.python|inc=*
-    - osplatform