fix(#176): last certification does postpone expiry

pallets/smith-members/src/lib.rs

@@ -455,7 +455,7 @@ impl<T: Config> Pallet<T> {
                         SmithStatus::Pending
                     };
 
-                if smith_meta.status == SmithStatus::Pending {
+                if previous_status != SmithStatus::Smith {
                     // - postpone the expiration: a Pending smith cannot do anything but wait
                     // this postponement is here to ease the process of becoming a smith
                     let new_expires_on =

pallets/smith-members/src/tests.rs

@@ -586,7 +586,6 @@ fn certifying_an_online_smith() {
             5
         ));
         // Smith can expire
-        // TODO: test failing because expires_on is not postponed to session 8
         assert_eq!(
             Smiths::<Runtime>::get(5),
             Some(SmithMeta {