llkd: do not crash kernel if llkd stops running

Today, assume llkd is not hardened enough to 100% guarantee that
lack of progress in inspection loops is a direct result of a
livelock condition affecting llkd itself.  Log a fatal alarm to
make init restart llkd instead for the time being.

ToDo: develop trust in llkd regarding sigalarm causes.

Test: compile
Bug: 119781757
Change-Id: I668dc1773898da6c95aad7221724b16f1684b067