logcat: fix logcatd / logpersist

Removing the rest of liblogcat broke logcatd since LogcatPanic() now
actually calls exit(), whereas logcatd relied on it to return
normally.

We can achieve the expected behavior with a small shell script, so
this change does that as well.

Test: logcatd / logpersist work
Change-Id: Icde36a4811a0db987a801978485e1af1dfc3d38c