tombstoned: temporarily allow write to anr_data_file.

auditallow this until we track down where the file is opened without
O_APPEND.

01-23 08:02:12.272   555   555 W tombstoned: type=1400 audit(0.0:11480): avc: denied { write } for path="/data/anr/traces.txt" dev="sda35" ino=4669445 scontext=u:r:tombstoned:s0 tcontext=u:object_r:anr_data_file:s0 tclass=file permissive=0

Bug: http://b/34193533
Test: mma
Change-Id: I77b854dce06231232004432839ebd5aa963ef035