Cache: Fix an issue with LRU when bonus block is used to complete transaction.

The block is never inserted because it's the one extra block in the cache, but
it can be invalidated twice in a row. In that case the block doesn't have a
new master id (beacuse it was never inserted), however it is valid and
the accounting goes wrong at that point.

src/mem/cache/cache_impl.hh

@@ -994,6 +994,7 @@ Cache<TagStore>::handleResponse(PacketPtr pkt)
         if (blk->isDirty()) {
             allocateWriteBuffer(writebackBlk(blk), time, true);
         }
+        blk->status &= ~BlkValid;
         tags->invalidateBlk(blk);
     }