request-ip should handle its own exception

Here's the related report: https://issues.guix.gnu.org/63158

This issue could possibly occur under these conditions:

• The connection lost due to unknown reasons (timeout, suddenly shutdown, etc...)
• Before the Ragnarok can handle the exception, request-ip was called, and getpeername throw exception that has no chance to be properly handled by Ragnarok.

Fix solution: catch exception inside requeest-ip and return unknown as the ip name.

This bug will be fixed after i18n branch merged.