Restore TestPullVerified test

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>

integration-cli/docker_cli_pull_test.go

@@ -55,8 +55,6 @@ func TestPullImageWithAliases(t *testing.T) {
 
 // pulling library/hello-world should show verified message
 func TestPullVerified(t *testing.T) {
-	t.Skip("problems verifying library/hello-world (to be fixed)")
-
 	// Image must be pulled from central repository to get verified message
 	// unless keychain is manually updated to contain the daemon's sign key.