Allow MediaProvider to bypass is_app_accessible_path checks

This allows MediaProvider doing an lstat(/mnt/user/0/emulated) to
succeed

Additionally, cached getuid() calls to reuse within the FUSE daemon

Test: presubmit
Bug: 170488060
Change-Id: I855b7c874a6f5b1dd5c9d39c58a9997ac6a64ce9
1 file changed