Do not hide user provided network mounts [v2]

Prevent the docker daemon from mounting the created network files over
those provided by the user via -v command line option. This would otherwise
hide the one provide by the user.
The benefit of this is that a user can provide these network files using the
-v command line option and place them in a size-limited filesystem.

Signed-off-by: Stefan Berger <stefanb@us.ibm.com>

integration-cli/docker_cli_run_test.go

@@ -2516,3 +2516,25 @@ func (s *DockerSuite) TestRunWriteFilteredProc(c *check.C) {
 		}
 	}
 }
+
+func (s *DockerSuite) TestRunNetworkFilesBindMount(c *check.C) {
+	testRequires(c, SameHostDaemon)
+	name := "test-nwfiles-mount"
+
+	f, err := ioutil.TempFile("", name)
+	c.Assert(err, check.IsNil)
+
+	filename := f.Name()
+	defer os.Remove(filename)
+
+	expected := "test123"
+
+	err = ioutil.WriteFile(filename, []byte(expected), 0644)
+	c.Assert(err, check.IsNil)
+
+	var actual string
+	actual, _ = dockerCmd(c, "run", "-v", filename+":/etc/resolv.conf", "busybox", "cat", "/etc/resolv.conf")
+	if actual != expected {
+		c.Fatalf("expected resolv.conf be: %q, but was: %q", expected, actual)
+	}
+}