Remove duplicate branches in request of plugins

[hrzlgnm]

The check for whether the name contains "ipv6" is not necessary for the plugins "dnshome" and "ipv64", as the code path for both branches is the same.
Furthermore the check is rather confusing in the context of the provider named "ipv64.net", as "ipv6" is also contained in the provider name itself.

[hrzlgnm]

I guess the same confusion applies to other constructs like for example in

inadyn/src/ddns.c

Line 139 in 46d6ad9

DO(http_init(client, "Checking for IP# change", strstr(provider->system->name, "ipv6") ? TCP_FORCE_IPV6 : TCP_FORCE_IPV4));

, causing ipv4 only updates fetching an ipv6 address from the default check server of the plugin for the provider ipv64.net. I would suggest to refine the check to check the prefix only, not the whole name.
Shall I open a separate issue for that case?

[troglobit]

Shall I open a separate issue for that case?

Yes, please do. Need to tread carefully around that legacy behavior, so that needs more review.