bees: use handle type for hash table extent locks

Fixes build breakage after "crucible: lockset: track lockers and use
handle type".

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

src/bees-hash.cc

@@ -311,7 +311,7 @@ BeesHashTable::fetch_missing_extent(HashType hash)
 	BEESNOTE("waiting to fetch hash extent #" << extent_number << ", " << missing_buckets << " left to fetch");
 
 	// Acquire blocking lock on this extent only
-	LockSet<uint64_t>::Lock extent_lock(m_extent_lock_set, extent_number);
+	auto extent_lock = m_extent_lock_set.make_lock(extent_number);
 
 	// Check missing again because someone else might have fetched this
 	// extent for us while we didn't hold any locks