Make sure amazon test doesn't check host keys

test/integration/Makefile

@@ -48,7 +48,7 @@ $(CREDENTIALS_FILE):
 	@exit 1
 
 amazon: $(CREDENTIALS_FILE)
-	ANSIBLE_SSH_PIPELINING=no BOTO_CONFIG=/dev/null ansible-playbook amazon.yml -i $(INVENTORY) -e @$(VARS_FILE) $(CREDENTIALS_ARG) -e "resource_prefix=$(CLOUD_RESOURCE_PREFIX)" -v $(TEST_FLAGS) ; \
+	ANSIBLE_HOST_KEY_CHECKING=False ANSIBLE_SSH_PIPELINING=no BOTO_CONFIG=/dev/null ansible-playbook amazon.yml -i $(INVENTORY) -e @$(VARS_FILE) $(CREDENTIALS_ARG) -e "resource_prefix=$(CLOUD_RESOURCE_PREFIX)" -v $(TEST_FLAGS) ; \
     RC=$$? ; \
     CLOUD_RESOURCE_PREFIX="$(CLOUD_RESOURCE_PREFIX)" make amazon_cleanup ; \
     exit $$RC;