readdir is safer than readdir_r.
readdir is safer than readdir_r.

The upstream cpplint.py already made this change.

Change-Id: I9614d51080557eab6730cffd476e01e7872729d0

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst