resolvectl: fix indentation of hexdump'ed packets
ebf963c551e1077abaa5e0fa0f330e6d1c23565e changed the 'sep' argument to always
be either " " or "\n", which broke the indentation logic for the first line
in base64_append_width(). Since it now always is one character, and never NULL,
let's change the type to char and simplify the logic a bit.
$ COLUMNS=30 build/test-dns-packet test/test-resolve/org~
20200417.pkts
============== test/test-resolve/org~
20200417.pkts ==============
org IN DNSKEY 256 3 RSASHA1-NSEC3-SHA1
AwEAAcLPVEcg0hFBheXQf
QOqqLiRgckk69o2KTAsq3
lNRY0c9mnEjzZDGsGmXNy
2EQ6yelkIYYus7KLor2Fz
x59hEqcM82zqkdHV6hXvZ
yjxxSHG3nl8xQS6gF8mdI
YouDTWWhTInfjSKoIeDok
Hq3S67EjSngV7/wVCMTbI
amS0NF4H
-- Flags: ZONE_KEY
-- Key tag: 37022
...
$ COLUMNS=120 build/test-dns-packet test/test-resolve/org~
20200417.pkts
============== test/test-resolve/org~
20200417.pkts ==============
org IN DNSKEY 256 3 RSASHA1-NSEC3-SHA1 AwEAAcLPVEcg0hFBheXQfQOqqLiRgckk69o2KTAsq3lNRY0c9mnEjzZDGsGmXNy2EQ6yelkIYYus7KLor
2Fzx59hEqcM82zqkdHV6hXvZyjxxSHG3nl8xQS6gF8mdIYouDTWWhTInfjSKoIeDokHq3S67EjSngV7/w
VCMTbIamS0NF4H
-- Flags: ZONE_KEY
-- Key tag: 37022
...