bpf: switch map/prog selinux_context field from storing 'fs_bpf_foo' to 'foo/'

This will eliminate the need for domain stuff.

After this:
  git grep fs_bpf_
finds nothing but comments.

Test: TreeHugger
Flag: EXEMPT no-op
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie834e9b2b120ee772690b28457c1ff080cb914dd
3 files changed