Update init.d script

The original init.d script uses a fixed username (e.g. git). Which is not flexible
when we using other user. So, I've updated it to use $APP_USER variable
instead and wrap it in a function to reduce repetitive codes.

lib/support/init.d/gitlab

@@ -16,6 +16,7 @@
 APP_ROOT="/home/git/gitlab"
+APP_USER="git"
 DAEMON_OPTS="-C $APP_ROOT/config/puma.rb -e production"
 PID_PATH="$APP_ROOT/tmp/pids"
 WEB_SERVER_PID="$PID_PATH/puma.pid"
@@ -36,6 +37,10 @@ check_pid(){
   fi
 }
+execute() {
+  sudo -u $APP_USER -H bash -l -c "$1"
+}
+
 start() {
   cd $APP_ROOT
   check_pid
@@ -45,8 +50,8 @@ start() {
     exit 1
   else
     if [ `whoami` = root ]; then
-      sudo -u git -H bash -l -c "RAILS_ENV=production bundle exec puma $DAEMON_OPTS"
-      sudo -u git -H bash -l -c "mkdir -p $PID_PATH && $START_SIDEKIQ  > /dev/null  2>&1 &"
+      execute "RAILS_ENV=production bundle exec puma $DAEMON_OPTS"
+      execute "mkdir -p $PID_PATH && $START_SIDEKIQ  > /dev/null  2>&1 &"
       echo "$DESC started"
     fi
   fi
@@ -58,7 +63,7 @@ stop() {
   if [ "$PID" -ne 0 -a "$STATUS" -ne 0 ]; then
     ## Program is running, stop it.
     kill -QUIT `cat $WEB_SERVER_PID`
-    sudo -u git -H bash -l -c "mkdir -p $PID_PATH && $STOP_SIDEKIQ  > /dev/null  2>&1 &"
+    execute "mkdir -p $PID_PATH && $STOP_SIDEKIQ  > /dev/null  2>&1 &"
     rm "$WEB_SERVER_PID" >> /dev/null
     echo "$DESC stopped"
   else
@@ -74,9 +79,9 @@ restart() {
   if [ "$PID" -ne 0 -a "$STATUS" -ne 0 ]; then
     echo "Restarting $DESC..."
     kill -USR2 `cat $WEB_SERVER_PID`
-    sudo -u git -H bash -l -c "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
-      sudo -u git -H bash -l -c "mkdir -p $PID_PATH && $START_SIDEKIQ  > /dev/null  2>&1 &"
+      execute "mkdir -p $PID_PATH && $START_SIDEKIQ  > /dev/null  2>&1 &"
     fi
     echo "$DESC restarted."
   else