llkd: Do not check apexd by default for stack

apexd is now blocked by sepolicy, so skip checking it to
prevent an avc warning.

See system/sepolicy commit ac097ac4c7718f8593f2b6b96a93a776984ec7c4

Addresses the following SELinux denial:

type=1400 audit(0.0:386): avc: denied { ptrace } for comm="llkd" scontext=u:r:llkd:s0 tcontext=u:r:apexd:s0 tclass=process permissive=0

Test: manual
Change-Id: Iad24447c8200e915ac8397a8f84923feebc20613