[0.18 backport] Make issuance fail for invalid addresses

[stevenroose]

Backport of #861.

[gwillen]

Diff looks the same as the backported MR:

bunneh:elements gwillen$ git range-diff upstream/pr/867^^..upstream/pr/867 upstream/pr/861^^..upstream/pr/861
1:  21b3913a7 = 1:  1b8bf85d8 Make issuance fail for invalid addresses
2:  8e5893ecb = 2:  425691623 Add test to make sure issuances to wrong addresses fail

(I guess that's a utACK? I'm never clear on how reviewing for backports is meant to work.)

[stevenroose]

Epic command!