cuckoo_table_db_test.cc: add flush after delete

It seems that a FlushMemTable() call is needed in the
Uint64Comparator test after call Delete(). Otherwise the later
via Put() added keys get lost with the next FlushMemTable()
call before the check.
Signed-off-by: NDanny Al-Gaaf <danny.al-gaaf@bisect.de>

db/cuckoo_table_db_test.cc

@@ -218,6 +218,7 @@ TEST(CuckooTableDBTest, Uint64Comparator) {
 
   // Add more keys.
   ASSERT_OK(Delete(Uint64Key(2)));  // Delete.
+  dbfull()->TEST_FlushMemTable();
   ASSERT_OK(Put(Uint64Key(3), "v0"));  // Update.
   ASSERT_OK(Put(Uint64Key(4), "v4"));
   dbfull()->TEST_FlushMemTable();