Update docker-py reqs in gate setup

TrivialFix

Change-Id: Idb0447a94a730fbcd822a855c865074817dd11b3

tests/setup_gate.sh

@@ -91,7 +91,7 @@ function setup_ansible {
     RAW_INVENTORY=/tmp/kolla/raw_inventory
     mkdir /tmp/kolla
 
-    sudo -H pip install "ansible<2" "docker-py>=1.4.0"
+    sudo -H pip install "ansible<2" "docker-py>=1.6.0"
 
     setup_inventory