Add RECEIVER_EXPORTED flags to screenshots

Builds on T+ require either the RECEIVER_EXPORTED or
RECEIVER_NOT_EXPORTED flag to be set when registering a broadcast
receiver. Recently a change went in to change from logging a
warning to throwing an error, causing sysui to crash when screenshots
are taken. This change adds the RECEIVER_EXPORTED flag to screenshot
code.

Bug: 213406883
Fix: 213406883
Test: verified that warnings no longer appear and sysui does not
crash when taking a screenshot

Change-Id: I0fa1c2272f1a994e51945be5f6c67cdccbb84cc2