filesystem: avoid duplicate change notifications
filesystem: avoid duplicate change notifications

 - Make sure to have only one GFileMonitor per directory

 - When deleting a directory avoid having both monitors
   (deleted dir's and its parent's) notifying it.

 - Fix typo causing notification when a monitor emits
   G_FILE_MONITOR_EVENT_CHANGES_DONE_HINT which happens
   after each set of changes.

https://bugzilla.gnome.org/show_bug.cgi?id=755181

GNOME/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,MikePetullo/grilo-plugins,MikePetullo/grilo-plugins,jasuarez/grilo-plugins,grilofw/grilo-plugins,GNOME/grilo-plugins