Clear calling identity when determining instant app status.

This requires INTERACT_ACROSS_USERS_FULL, which the current caller
(MediaProvider) lacks.

Bug: 199988018
Test: inspect logs
Change-Id: I4ef3494315b996473a0fb14b967ddaf62b5d7aa6

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

@@ -4366,8 +4366,13 @@ class StorageManagerService extends IStorageManager.Stub
                 packageName = packagesForUid[0];
             }
 
-            if (mPmInternal.isInstantApp(packageName, UserHandle.getUserId(uid))) {
-                return StorageManager.MOUNT_MODE_EXTERNAL_NONE;
+            final long token = Binder.clearCallingIdentity();
+            try {
+                if (mPmInternal.isInstantApp(packageName, UserHandle.getUserId(uid))) {
+                    return StorageManager.MOUNT_MODE_EXTERNAL_NONE;
+                }
+            } finally {
+                Binder.restoreCallingIdentity(token);
             }
 
             if (mStorageManagerInternal.isExternalStorageService(uid)) {