Fix concurrent GC to properly handle no zygote.
Fix concurrent GC to properly handle no zygote.

I had introduced a regression in
https://googleplex-android-review.googlesource.com/#/c/389851/
which caused concurrent GC to not get run if there was no zygote.
This caused a regression in ritzperf when run from the commmand
line. The fix properly handles the no zygote case by doing full
GC instead.

Bug: 11811477
Change-Id: Ib42b914509b951054895fea8741f6c68cdada52a

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst