Skip remountUid for system_server

Several processes share the system_server uid. Since it has
all access it wants. No need to remountUid for apps sharing that uid
Test: manual
Bug: 141678467
Change-Id: Iab35e41d54e4d82eccfc8d8ca052aa93157e8b49

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

@@ -2203,6 +2203,11 @@ class StorageManagerService extends IStorageManager.Stub
     }
 
     private void remountUidExternalStorage(int uid, int mode) {
+        if (uid == Process.SYSTEM_UID) {
+            // No need to remount uid for system because it has all access anyways
+            return;
+        }
+
         try {
             mVold.remountUid(uid, mode);
         } catch (Exception e) {