* [service] Restart SwSS Docker container if orchagent exits unexpectedly
* Configure systemd to stop restarting swss if it attempts to restart more than 3 times in 20 minutes
* Move supervisor-proc-exit-listener script
* [docker-dhcp-relay] Enhance wait_for_intf.sh.j2 to utilize STATEDB
* Ensure dependent services stop/start/restart with SwSS
* Change 'StartLimitInterval' to 'StartLimitIntervalSec', as Stretch installs systemd 232 (>= v230)
* Also update journald.conf options
* Remove 'PartOf' option from unit files
* Add '$(SUPERVISOR_PROC_EXIT_LISTENER_SCRIPT)' to new shared docker-orchagent makefile
* Make supervisor-proc-exit-listener script read from 'critical_processes' file inside container
* Update critical_processes file for swss container
