Fix some lint warning and simplify some code

src/database/mod.rs

@@ -144,9 +144,7 @@ pub mod testhelpers {
                 .user_map
                 .borrow()
                 .iter()
-                .filter(|u| u.username == user && u.password == pass)
-                .collect::<Vec<&User>>()
-                .first()
+                .find(|&u| u.username == user && u.password == pass)
             {
                 Some(u) => {
                     let copy = (*u).clone();
@@ -160,9 +158,7 @@ pub mod testhelpers {
             self.user_map
                 .borrow()
                 .iter()
-                .filter(|u| u.username == user)
-                .collect::<Vec<&User>>()
-                .first()
+                .find(|&u| u.username == user)
                 .is_some()
         }
     }