sock_addr_validate: remove redundant expression

[gperciva]

No description provided.

[gperciva]

Whoops, this slipped through the cracks.

I normally run clang-tidy for new features, but to save time I omit libcperciva/ files from the check because I figure those files will be checked when I run clang-tidy in that repository.

Then when I was importing this change to libcperciva, I didn't bother with clang-tidy because it was only importing a commit, not "new" code.

[cperciva]

The original code was redundant but was easier to understand -- "check for a missing hostname" doesn't make sense by itself since local socket paths don't have hostnames. We can change the code if you want to keep clang-tidy happy but the comment should explain that local socket paths will pass the test since they start with /.

[gperciva]

Ok, revised comment. It feels a bit wordy, but I couldn't think of a shorter way without ambiguity.

In case you were wondering: I disable approximately 70 clang-tidy checks; the remainder are ones which I think could give useful warnings in some cases.