Fix the `service gitlab restart` command

This commit addresses two related issues:
- Sidekiq should shut down completely before we restart it;
- If we restart unicorn with USR2 we need to kill the old master and
  worker processes.

config/unicorn.rb.example

@@ -64,19 +64,19 @@ before_fork do |server, worker|
   # installations.  It is not needed if your system can house
   # twice as many worker_processes as you have configured.
   #
-  # # This allows a new master process to incrementally
-  # # phase out the old master process with SIGTTOU to avoid a
-  # # thundering herd (especially in the "preload_app false" case)
-  # # when doing a transparent upgrade.  The last worker spawned
-  # # will then kill off the old master process with a SIGQUIT.
-  # old_pid = "#{server.config[:pid]}.oldbin"
-  # if old_pid != server.pid
-  #   begin
-  #     sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
-  #     Process.kill(sig, File.read(old_pid).to_i)
-  #   rescue Errno::ENOENT, Errno::ESRCH
-  #   end
-  # end
+  # This allows a new master process to incrementally
+  # phase out the old master process with SIGTTOU to avoid a
+  # thundering herd (especially in the "preload_app false" case)
+  # when doing a transparent upgrade.  The last worker spawned
+  # will then kill off the old master process with a SIGQUIT.
+  old_pid = "#{server.config[:pid]}.oldbin"
+  if old_pid != server.pid
+    begin
+      sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
+      Process.kill(sig, File.read(old_pid).to_i)
+    rescue Errno::ENOENT, Errno::ESRCH
+    end
+  end
   #
   # Throttle the master from forking too quickly by sleeping.  Due
   # to the implementation of standard Unix signal handlers, this

lib/support/init.d/gitlab

@@ -81,7 +81,7 @@ restart() {
   if [ "$PID" -ne 0 -a "$STATUS" -ne 0 ]; then
     echo "Restarting $DESC..."
     kill -USR2 `cat $WEB_SERVER_PID`
-    execute "mkdir -p $PID_PATH && $STOP_SIDEKIQ  > /dev/null  2>&1 &"
+    execute "mkdir -p $PID_PATH && $STOP_SIDEKIQ  > /dev/null  2>&1"
     if [ `whoami` = root ]; then
       execute "mkdir -p $PID_PATH && $START_SIDEKIQ  > /dev/null  2>&1 &"
     fi