server domain workaround for single server portals

[kwypchlo]

explanation and motivation in code description

note: nginx will throw warnings on startup for single server portals but it's expected, it just means there are 2 blocks with the same server name and the latter is going to be ignored (which is a wanted outcome)

nginx            | nginx: [warn] conflicting server name "account.siasky.xyz" on 0.0.0.0:80, ignored
nginx            | nginx: [warn] conflicting server name "siasky.xyz" on 0.0.0.0:80, ignored
nginx            | nginx: [warn] conflicting server name "*.hns.siasky.xyz" on 0.0.0.0:80, ignored
nginx            | nginx: [warn] conflicting server name "*.siasky.xyz" on 0.0.0.0:80, ignored
nginx            | nginx: [warn] conflicting server name "account.siasky.xyz" on 0.0.0.0:443, ignored
nginx            | nginx: [warn] conflicting server name "siasky.xyz" on 0.0.0.0:443, ignored
nginx            | nginx: [warn] conflicting server name "*.hns.siasky.xyz" on 0.0.0.0:443, ignored
nginx            | nginx: [warn] conflicting server name "*.siasky.xyz" on 0.0.0.0:443, ignored