elements-0.21 vs master incompatibility

[ajtowns]

I was trying out liquidtestnet and found I couldn't actually maintain a connection to anyone. I believe this is due to bitcoin/bitcoin#20564 having been backported to elements-0.21 in #1029 but not ported to master yet. Tweaking the code locally did indeed successfully work around the problem.

[apoelstra]

Thanks! Will be fixed then by the 22 rebase #1058 then I expect.