Send DROPBOX_ENTRY_ADDED to all users

- DROPBOX_ENTRY_ADDED is sent to the system user.
- In headless system user, the current user could not be the system
user.
- This CL make it broadcasted to all interested receivers.

Bug: 158246058
Test: atest
CtsAppExitTestCases: android.app.cts.ActivityManagerAppExitInfoTest#testAnr
Change-Id: I897782a809ef5a115c536b03348296bdc4166630