Terminate corfu java process in a cleaner way (#747)

This patch re-implements the logic to kill java process when corfu server
is told to exit by systemd. The new logic is much cleaner and easier
to understand.

Note this patch breaks the support to kill java process properly for
non-systemd environments, which are mostly obsolete in debian ecosystem.

debian/src/deb/init.d/corfu-server

@@ -21,18 +21,9 @@ LOGFILE="/var/log/corfu.$PORT.log"
 
 export PATH="${PATH:+$PATH:}/usr/sbin/:usr/bin"
 
-terminate_java_process () {
-    # save default shell delimiter
-    SAVED_IFS=$IFS
-    IFS=$'\n'
-    ALL_PROCESSES=$(ps aux)
-    for line in $ALL_PROCESSES; do
-        if [[ $line == *"org.corfudb.infrastructure.CorfuServer"* ]]; then
-            # send SIGTERM to JVM
-            kill -15 $(echo $line | awk '{print $2}')
-        fi
-    done
-    IFS=$SAVED_IFS
+terminate_corfu_process () {
+    # send SIGTERM to each process under corfu-server systemd service.
+    ps awx -eo pid,cgroup | grep corfu-server.service | awk '{print $1}' | xargs -n 1 kill &> /dev/null
 }
 
 case "$1" in
@@ -47,7 +38,7 @@ case "$1" in
         ;;
     stop)
         log_daemon_msg "Stopping $ROLENAME on port $PORT"
-        terminate_java_process
+        terminate_corfu_process
         if start-stop-daemon --stop --quiet  --oknodo --pidfile $PIDFILE; then
             log_end_msg 0
         else
@@ -57,7 +48,7 @@ case "$1" in
     restart)
         log_daemon_msg "Restarting $ROLENAME on port $PORT"
         set +e
-        terminate_java_process
+        terminate_corfu_process
         start-stop-daemon --stop --quiet --retry 30 --pidfile $PIDFILE
         RET="$?"
         set -e