Make TestContext.RegisterModuleType take an android.ModuleFactory

Avoid having to pass ModuleFactoryAdaptor to every call to
RegisterModuleType in a test by wrapping RegisterModuleType.

Test: all soong tests
Change-Id: If8847d16487de0479cc3020b728256922b3cadba
diff --git a/xml/xml_test.go b/xml/xml_test.go
index f2a440f..0a11566 100644
--- a/xml/xml_test.go
+++ b/xml/xml_test.go
@@ -50,8 +50,8 @@
 func testXml(t *testing.T, bp string) *android.TestContext {
 	config := android.TestArchConfig(buildDir, nil)
 	ctx := android.NewTestArchContext()
-	ctx.RegisterModuleType("prebuilt_etc", android.ModuleFactoryAdaptor(android.PrebuiltEtcFactory))
-	ctx.RegisterModuleType("prebuilt_etc_xml", android.ModuleFactoryAdaptor(PrebuiltEtcXmlFactory))
+	ctx.RegisterModuleType("prebuilt_etc", android.PrebuiltEtcFactory)
+	ctx.RegisterModuleType("prebuilt_etc_xml", PrebuiltEtcXmlFactory)
 	ctx.Register()
 	mockFiles := map[string][]byte{
 		"Android.bp": []byte(bp),