dragonball: Remove unnecessary unwrap

Given that we call `is_some` earlier, we don't then need to unwrap,
so refactor to avoid this

Signed-off-by: stevenhorsman <steven@uk.ibm.com>

src/dragonball/dbs_virtio_devices/src/vhost/vhost_user/connection.rs

@@ -352,8 +352,7 @@ impl Endpoint {
         // base is not zero any more. So don't set queue base on reconnection.
         // N.B. it's really TDD, we just found it works in this way. Any spec about this?
         for queue_index in 0..queue_num {
-            let base = if old.is_some() {
-                let conn = old.as_mut().unwrap();
+            let base = if let Some(conn) = &mut old {
                 match conn.get_vring_base(queue_index) {
                     Ok(val) => Some(val),
                     Err(_) => None,