crimson/os/seastore/cache: set extent's state to INVALID when invalidating it

Previously, when invalidating a non-conflict extent, I forgot to set its state

Signed-off-by: Xuehan Xu <xxhdx1985126@gmail.com>

src/crimson/os/seastore/cache.cc

@@ -804,6 +804,7 @@ void Cache::invalidate_extent(
 {
   if (!extent.may_conflict()) {
     assert(extent.transactions.empty());
+    extent.state = CachedExtent::extent_state_t::INVALID;
     return;
   }