logcat: -d, -t or -L, along with -f, do not background

Specifically logcatd with exec logcat -L needs to be foreground
process cgroup as it is spawned and can block init progress. Makes
sense generally to only set background cgroup when we are taking
continuous content, and we are pushing that content to a set of
logrotate files.

Rename setupOutput to setupOutputAndSchedulingPolicy to more
clearly indicate its purpose.

Bug: 30630936
Bug: 30612424
Bug: 28788401
Change-Id: I628d590a42a53a6b448ecd0af53d6d1edf7bbb0e