StorageHostTest: scan after renaming a file.

A recent optimization that bypasses database operations for apps with
MANAGE_EXTERNAL_STORAGE caused the quota tests to break, since quota is
updated as a part of these same database operations.

Explicitly ask MediaStore to scan, to ensure the quota is up-to-date.

Bug: 166062499
Test: atest
android.appsecurity.cts.StorageHostTest#testVerifyStatsExternal

Change-Id: I34e360b648137327fab401a0f69083883744d4e7