Refactors is_banned logic and forces health check on unban (#288)

* Refactors is_banned logic and forces healthcheck on unban

* typo

* Make is banned log debug

* addressing comments

* Comment

src/query_router.rs

@@ -774,6 +774,7 @@ mod test {
             automatic_sharding_key: Some(String::from("id")),
             healthcheck_delay: PoolSettings::default().healthcheck_delay,
             healthcheck_timeout: PoolSettings::default().healthcheck_timeout,
+            ban_time: PoolSettings::default().ban_time,
         };
         let mut qr = QueryRouter::new();
         assert_eq!(qr.active_role, None);