Only try to kill ssl listener process at first

Previously service xcatd stop or systemctl stop xcatd.service
will send TERM signal to all the processes of xcatd on some
platform which support this feature.

Close-issue: #1008 #537

xCAT-server/etc/init.d/xcatd

@@ -101,7 +101,7 @@ stop)
     echo
     exit 0
   fi
-  kill -TERM -`cat /var/run/xcatd.pid`
+  kill -TERM `cat /var/run/xcatd.pid`
   i=0;
   while $STATUS > /dev/null 2>&1 && [ $i -lt 30 ]; do
     sleep .1