Revert "Freeze all package processes before killing"

This reverts commit 6eff4d8f.

Reason for revert: b/236266655 zygote for a new process spawns in different process group before moving, which causes permanent freeze of all zygote processes.

Change-Id: Icd245a3a23bda26659b81a8b5b24682655649222
(cherry picked from commit 14c64e26)
Merged-In: Icd245a3a23bda26659b81a8b5b24682655649222