Supplemental processes don't get external storage.

Bug: 217538016
Test: Inspect /storage for supplemental
Change-Id: Ibd29834b0d611a7313890fe06428cd73021ebf4f

core/java/android/os/Environment.java

@@ -1333,7 +1333,7 @@ public class Environment {
         final Context context = AppGlobals.getInitialApplication();
         final int uid = context.getApplicationInfo().uid;
         // Isolated processes and Instant apps are never allowed to be in scoped storage
-        if (Process.isIsolated(uid)) {
+        if (Process.isIsolated(uid) || Process.isSupplemental(uid)) {
             return false;
         }
 

services/core/java/com/android/server/StorageManagerService.java

@@ -4674,7 +4674,7 @@ class StorageManagerService extends IStorageManager.Stub
     private int getMountModeInternal(int uid, String packageName) {
         try {
             // Get some easy cases out of the way first
-            if (Process.isIsolated(uid)) {
+            if (Process.isIsolated(uid) || Process.isSupplemental(uid)) {
                 return StorageManager.MOUNT_MODE_EXTERNAL_NONE;
             }