the jetty user is listed in the gdm login screen
id is below 1000, not sure why it is listed.
[paolo@murdock ~]$ id jetty
uid=992(jetty) gid=989(jetty) groups=989(jetty)
this was fixed in upstream gdm
*** Bug 813879 has been marked as a duplicate of this bug. ***
*** Bug 815177 has been marked as a duplicate of this bug. ***