opcode/opcodeflg tests report timeout when server does not copy opcode

$ dig a tdns.powerdns.org @127.0.0.1 +opcode=15 +noedns +nodnssec +ignore

; <<>> DiG 9.11.2 <<>> a tdns.powerdns.org @127.0.0.1 +opcode=15 +noedns +nodnssec +ignore
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOTIMP, id: 24795
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;tdns.powerdns.org.		IN	A

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Fri Apr 13 17:56:42 CEST 2018
;; MSG SIZE  rcvd: 35

Note that the server did not copy the opcode to the response. In this case, genreport apparently does not match the response to the query, unhelpfully reporting timeout.