Spurious warnings on sockets cause clam(d)scans to fail #1672

1. Problem: ClamAV cannot handle unix sockets in general, and throws a WARNING about an unsupported file type (which is wrong, sockets are not files)
2. Problem: ClamAV interacts even more poorly with bind mounted sockets (which is the canonical solution to e.g. allowing chroot'd openssh sftp instances to log file transfers) and throws a "failed to open file error"
3. Problem: These cause clam(d)scan to terminate with hard errors (even though 1. claims to be a "warning")

Since sockets aren't files and there is no way for clamav to ever handle sockets, they should simply be silently skipped over, instead of attempting to do anything with them.

Especially since it is impossible to come up with safe regexes to exclude sockets and only sockets, because you can create them under arbitrary path names in arbitrary locations.