Merge component 'engine' from [email protected]:docker/engine master

Author: GordonTheTurtle

components/engine/integration-cli/docker_utils_test.go

@@ -63,7 +63,7 @@ func getContainerCount(c *check.C) int {
 	for _, line := range lines {
 		if strings.Contains(line, containers) {
 			output := strings.TrimSpace(line)
-			output = strings.TrimLeft(output, containers)
+			output = strings.TrimPrefix(output, containers)
 			output = strings.Trim(output, " ")
 			containerCount, err := strconv.Atoi(output)
 			assert.NilError(c, err)