Merge "CtsTestServer: Add access to assets in external storage directory" am: 62569ba06e am: fb545b29c1 am: 8910c2d43d am: 17dd4813fc

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

Change-Id: Ib61ccdf9133f3e1415151c1707d5e9688a68965a