Add better output for TestLinksEtcHostsContentMatch to help debug #14774

Signed-off-by: Doug Davis <dug@us.ibm.com>

integration-cli/docker_cli_links_unix_test.go

@@ -27,7 +27,7 @@ func (s *DockerSuite) TestLinksEtcHostsContentMatch(c *check.C) {
 	}
 
 	if out != string(hosts) {
-		c.Errorf("container")
+		c.Errorf("container: %s\n\nhost:%s", out, hosts)
 	}
 
 }