init: Treat failure to create a process group as fatal

During process startup, system creates a process group and places the
new process in it. If process group creation fails for some reason, the
new child process will stay in its parent's group. This poses danger
when the child is being frozen because the whole group is affected and
its parent is being frozen as well.
Fix this by treating group creation failure as a fatal error which would
prevent the app from starting.

Bug: 227395690
Test: fake group creation failure and confirm service failure to start
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I83261bef803751759c7fd709bf1ccd33ccad3a0b