plugins_page: change the return value of rank() from "-1" into "300"

Change-Id: I70f69e1f93cda0c1ac0f77a2ad5ccc0862e6ae54
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1011765
Signed-off-by: hadong <hadong0720@gmail.com>