Add build integration cli tests

Clean up tests to remove duplicate code

Add tests which run pull and create in an isolated configuration directory.
Add build test for untrusted tag

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

integration-cli/docker_cli_push_test.go

@@ -281,7 +281,7 @@ func (s *DockerTrustSuite) TestTrustedPushWithIncorrectPassphraseForNonRoot(c *c
 		c.Fatalf("Error missing from trusted push with short targets passphrase: \n%s", out)
 	}
 
-	if !strings.Contains(string(out), "Password Invalid, operation has failed") {
+	if !strings.Contains(string(out), "password invalid, operation has failed") {
 		c.Fatalf("Missing expected output on trusted push with short targets/snapsnot passphrase:\n%s", out)
 	}
 }