Historically we pushed all system_server SD card interactions through
DefaultContainerService to avoid holding open FDs, but it's safe to
measure disk usage for internal emulated storage when looking
directly at /data/media, since there is no risk of unsafe ejection.

These rule changes give us just enough access to measure statistics.

avc: denied { getattr } for path="/data/media/0/DCIM/.thumbnails" dev="sda35" ino=589892 scontext=u:r:system_server:s0 tcontext=u:object_r:media_rw_data_file:s0:c512,c768 tclass=dir permissive=1
avc: denied { open } for path="/data/media/0/DCIM/.thumbnails" dev="sda35" ino=589892 scontext=u:r:system_server:s0 tcontext=u:object_r:media_rw_data_file:s0:c512,c768 tclass=dir permissive=1
avc: denied { read } for name="0" dev="sda35" ino=589827 scontext=u:r:system_server:s0 tcontext=u:object_r:media_rw_data_file:s0 tclass=dir permissive=1

Test: builds, boots, and access allowed
Bug: 33298975
Change-Id: I9748608a5c1169d542e763c5a8f79c4f26f7a382