Fix SELinux "could not set" errors.

A previous commit reverted us back to using file_contexts
instead of genfs_contexts but did not remove the new
genfs_contexts rules, which caused this problem.

Bug: 62901680
Test: Verified that the errors do not apepar and that wifi
and traceur work.

Change-Id: Ic0078dc3a2a9d3d35a10599239fdf9fa478f1e2b