e exec tracker - fix tracking to update desktop files on efreet change
e exec tracker - fix tracking to update desktop files on efreet change

efreet will send change events meaning out desktop file icons are
invalid now. we have refs but content is junk. update these to new
desktop ptr handles by using the exec key to look up new ones on the
change event. this fixes ibar gainign a bunch of blank unknown icons
when any desktop files are touched on the system or user dirs

@fix

rvandegrift/e,rvandegrift/e,rvandegrift/e