Fix 'tcp+tls' protocol not being accepted

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

urlutil/urlutil_test.go

@@ -18,6 +18,12 @@ var (
 	invalidGitUrls = []string{
 		"http://github.com/docker/docker.git:#branch",
 	}
+	transportUrls = []string{
+		"tcp://example.com",
+		"tcp+tls://example.com",
+		"udp://example.com",
+		"unix:///example",
+	}
 )
 
 func TestValidGitTransport(t *testing.T) {
@@ -53,3 +59,11 @@ func TestIsGIT(t *testing.T) {
 		}
 	}
 }
+
+func TestIsTransport(t *testing.T) {
+	for _, url := range transportUrls {
+		if IsTransportURL(url) == false {
+			t.Fatalf("%q should be detected as valid Transport url", url)
+		}
+	}
+}