outdated DNS seed for SPV

[FirstClassCitizenFCC]

What happened:

If bitseed.xf2.org is the only DNS seed available for SPV, running defid results in sending multiple (25-30) DNS queries per second.

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

• block all seeds from BRMainNetDNSSeeds except bitseed.xf2.org
• run defid

What are your environment parameters:

docker defi/defichain:latest

Anything else we need to know?:

• Allowing all DNS seeds resolved the issue.
• Bitcoin Core removed this seed in #9730
• dns query-status is SERVFAIL

# dig @1.1.1.1 bitseed.xf2.org

; <<>> DiG 9.16.15-Debian <<>> @1.1.1.1 bitseed.xf2.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 44015
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; EDE: 22 (No Reachable Authority)
;; QUESTION SECTION:
;bitseed.xf2.org.		IN	A

;; Query time: 32 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Fri Jan 07 18:44:36 CET 2022
;; MSG SIZE  rcvd: 50

[defichain-bot]

@FirstClassCitizenFCC: Thanks for opening an issue, it is currently awaiting triage.

The triage/accepted label can be added by foundation members by writing /triage accepted in a comment.

Details

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[prasannavl]

Thanks @FirstClassCitizenFCC. Add to high priority lists for v3, where ICX is planned to be re-enabled.