PRODUCT_MANIFEST_PACKAGE_NAME_OVERRIDES is applicable to override_apex

apex { name: "foo" }
override_apex { name: "override_foo", base:"foo" }

PRODUCT_MANIFEST_PACKAGE_NAME_OVERRIDES := foo:com.android.foo

Previously, the override was done only for the overridden package "foo",
but not for "override_foo". Fixing this issue by using ctx.ModuleName()
when finding the package name to use.

Bug: 150645663
Test: m
Change-Id: I2947e5c75369216a4bbce8749503236be86771c3
diff --git a/apex/builder.go b/apex/builder.go
index 2701a36..af27751 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -649,7 +649,7 @@
 		}
 		return ""
 	}
-	manifestPackageName, overridden := ctx.DeviceConfig().OverrideManifestPackageNameFor(a.Name())
+	manifestPackageName, overridden := ctx.DeviceConfig().OverrideManifestPackageNameFor(ctx.ModuleName())
 	if overridden {
 		return manifestPackageName
 	}