MB-46365: Print opcode as int

The test harness uses Invalid opcode which breaks the history
dump due to to_string throwing.

Change-Id: I7d7e462d1d6c9f08c3c6cd9d960d63a0fc2d94b1
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/156249
Reviewed-by: Dave Rigby <[email protected]>
Tested-by: Build Bot <[email protected]>

Author: jimwwalker

engines/ep/tests/ep_testsuite_dcp.cc

@@ -438,7 +438,7 @@ void TestDcpConsumer::run(bool openConn) {
                           << std::endl;
                 std::cerr << "DCP history:" << std::endl;
                 for (auto entry : history) {
-                    std::cerr << entry.first << " " << entry.second
+                    std::cerr << int(entry.first) << " " << entry.second
                               << std::endl;
                 }
                 check(false, "Aborting");