Regression in IPv6 parsing in ssh_options_set API

We were made aware of failing tests in Cockpit with the new libssh release:

https://build.opensuse.org/request/show/1134431#comment-1862999

https://github.com/cockpit-project/cockpit/issues/19772

The problem is that the bare IPv6 addresses are now confused with the syntax host:port which make the parsing of ::1 fail inside of ssh_options_set() API, which was part of refactoring in b83368b2 and which we missed as part of reviews.

I am working on a fix.