[#660] writecache: Fix remaining addr2key uses

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/local_object_storage/writecache/writecachebadger/flush_test.go

@@ -52,8 +52,9 @@ func TestFlush(t *testing.T) {
 			Desc: "db, invalid object",
 			InjectFn: func(t *testing.T, wc writecache.Cache) {
 				c := wc.(*cache)
+				key := addr2key(oidtest.Address())
 				require.NoError(t, c.db.Update(func(tx *badger.Txn) error {
-					return tx.Set([]byte(oidtest.Address().EncodeToString()), []byte{1, 2, 3})
+					return tx.Set(key[:], []byte{1, 2, 3})
 				}))
 			},
 		},