Comment 7 for bug 1818527

Sponsored in Bionic.

* The fix LGTM.
- Looking in systemd git upstream repo, I couldn't find anything (revert, known regression introduced by this particular fix or else)
- I easily reproduced the bug using systemd without the fix, and I confirm it works for both enumerated scenarios found in [Test Case] just fine[0] with the fix.
- This has been extensively tested in both upstream and other Debian/Ubuntu releases.

* Very minor modifications:
- Slightly modified the DEP3 header (Adding the upstream bug link, ....)
- Renamed the patch from "lp1818527-resolved-do-not-hit-CNAME-in-NODATA.patch" to "resolved-do-not-hit-CNAME-in-NODATA.patch" to stay consistent with current other "resolved" patch type.

Thanks Heitor for your contribution.

- Eric

[0] - Validation of the fix in Bionic:
# systemd-resolve --flush-caches
# dig github.com -t CNAME

; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> github.com -t CNAME
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8781
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;github.com. IN CNAME

;; Query time: 22 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Tue Jun 11 15:43:51 EDT 2019
;; MSG SIZE rcvd: 39

# dig github.com

; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> github.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2811
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;github.com. IN A

;; ANSWER SECTION:
github.com. 42 IN A 192.30.253.113

;; Query time: 13 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Tue Jun 11 15:43:55 EDT 2019
;; MSG SIZE rcvd: 55