fuse: Do not unref result of g_vfs_get_default
fuse: Do not unref result of g_vfs_get_default

Result from g_vfs_get_default shouldn't be freed as per documentation.

https://bugzilla.gnome.org/show_bug.cgi?id=762250

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