[DO NOT MERGE] OPP: append timestamp to the file name

Bluetooth stores received files using contentResolver.insert(), which
only allows up to 32 instances with the same file name. Append timestamp
to the file name to prevent IllegalStateException.

Bug: 161651809
Test: manual
Change-Id: I7f75fb96ec4fc33da2a4714e1446935052a9c156
1 file changed