Revert "Add override_module."

This reverts commit aa65e17016.

Reason for revert: Not compatible with PRODUCT_PACKAGES, and so has very limited use.

Change-Id: Ib141d3984a6f12bb50989e66037494c466b066f1

java/app.go

@@ -392,7 +392,7 @@ func (a *AndroidApp) collectAppDeps(ctx android.ModuleContext) ([]jniLib, []Cert
 func (a *AndroidApp) getCertString(ctx android.BaseContext) string {
 	certificate, overridden := ctx.DeviceConfig().OverrideCertificateFor(ctx.ModuleName())
 	if overridden {
-		return certificate
+		return ":" + certificate
 	}
 	return String(a.appProperties.Certificate)
 }