To write bytes to appfuse file from priv_app, we need to specify
mlstrustedobject.
The CL fixes the following denial.

type=1400 audit(0.0:77): avc: denied { write } for name="10" dev="fuse" ino=10 scontext=u:r:priv_app:s0:c512,c768 tcontext=u:object_r:app_fuse_file:s0 tclass=file permissive=0

BUG=23093747

(cherry picked from commit 4d19f98c)

Change-Id: I9901033bb3349d5def0bd7128db45a1169856dc1