Migrate some integration-cli test to api tests

This fix migrate  TestLinksEtcHostsContentMatch
to api test.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: e6bd20edcbf3b7a6f87a356ab0943714936c70e1
Component: engine

components/engine/integration-cli/docker_cli_links_unix_test.go

@@ -1,26 +0,0 @@
-// +build !windows
-
-package main
-
-import (
-	"io/ioutil"
-	"os"
-
-	"github.com/docker/docker/integration-cli/checker"
-	"github.com/go-check/check"
-)
-
-func (s *DockerSuite) TestLinksEtcHostsContentMatch(c *check.C) {
-	// In a _unix file as using Unix specific files, and must be on the
-	// same host as the daemon.
-	testRequires(c, SameHostDaemon, NotUserNamespace)
-
-	out, _ := dockerCmd(c, "run", "--net=host", "busybox", "cat", "/etc/hosts")
-	hosts, err := ioutil.ReadFile("/etc/hosts")
-	if os.IsNotExist(err) {
-		c.Skip("/etc/hosts does not exist, skip this test")
-	}
-
-	c.Assert(out, checker.Equals, string(hosts), check.Commentf("container: %s\n\nhost:%s", out, hosts))
-
-}