trash: Check modification time to avoid rereading
trash: Check modification time to avoid rereading

Rereading of trash dirs is pretty expensive and unfortunately it is
performed more often with recent changes. Check modification time of
each trash dir in order to avoid needless rereading, because simple
query_info call is much faster than enumeration.

https://bugzilla.gnome.org/show_bug.cgi?id=711459

gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs