Simplify implementation of ContactStore::all_contacts()

This way we alter the underlying iterator for all contacts to only
iterate in the "contact" collection of the store, which results in fewer
disk access because the internal iterator does not yield all pathes from
the store before filtering them.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

lib/domain/libimagcontact/src/store.rs

@@ -77,15 +77,7 @@ impl<'a> ContactStore<'a> for Store {
     }
 
     fn all_contacts(&'a self) -> Result<StoreIdIterator> {
-        let iter = self
+        self.entries().map(|iter| iter.in_collection("contact").without_store())
-            .entries()?
-            .without_store()
-            .filter(|id| match *id {
-                Ok(ref id) => id.is_in_collection(&["contact"]),
-                Err(_) => true,
-            });
-
-        Ok(StoreIdIterator::new(Box::new(iter)))
     }
 
 }