Merge "CtsTestServer: Add access to assets in external storage directory" am: 62569ba06e am: fb545b29c1 am: 8910c2d43d

Original change: https://android-review.googlesource.com/c/platform/cts/+/1423852

Change-Id: Ia82f4af96bfe2272ddf7bde143640521c570c04c