This commit moves parent pid process from the webapp package to the boot
script. This means that daemonized apps without webapp will also exit
when the runner exits, if run from the runner. (For example, several
self-tests such as 'autoupdate' no longer leak node processes.) This is
controlled via the $METEOR_PARENT_PID environment variable instead of
from command line arguments, in order to make fewer assumptions about
how Meteor apps process arguments.
This also drops the old --keepalive support (which already has stopped
being used by the dev mode runner or any MDG deployment platforms).
Neither --parent-pid nor --keepalive were documented beforehand, and
--keepalive was already deprecated before 1.0.
These flags used to also incidentally trigger printing the LISTENING
line; this is now controlled by $METEOR_PRINT_ON_LISTEN.
Fixes#3315.
096df9d62d