Fix dispatching of gpollfd sources

Closes: #1592 (closed)

GLib skips pollfd sources when there is at least 1 timer source ready with priority higher than default one.

This seems to be introduced in https://bugzilla.gnome.org/show_bug.cgi?id=11059 which changed sorting order of poll records.

The change fixes this by traversing through poll records untill ready fd is found.