syslogd use "non-string" instead of panicking if the workload or any …

…system component logs non string.

Folks from other team reached out to me to see if I have seen an issue where syslogd crashes (they were trying to debug but they couldn't get the logs).
Surely enough it was very easy to reproduce.
Just add the following to the workload:
LOG(INFO) << "\x01\x02\x03\x04\x05\x06\x01\xff\xff\xff\xff";

https://screenshot.googleplex.com/5XAgWWpxZVZZJ9h

Not sure what is the best way to handle string conversion errors here, should we bail from the function ? or just pass in "non-string".
Feedbacks are greatly appreciated.

Change-Id: I6b7186dcdc2df935e1b84d9c3a1afa260f09d295

oak_containers/syslogd/src/systemd_journal.rs

@@ -146,8 +146,8 @@ impl Journal {
                     let (name, value) =
                         field.split_at(field.iter().position(|x| *x == b'=').unwrap_or(0));
                     fields.insert(
-                        std::str::from_utf8(name).unwrap().to_string(),
-                        std::str::from_utf8(&value[1..]).unwrap().to_string(),
+                        std::str::from_utf8(name).unwrap_or("non-string").to_string(),
+                        std::str::from_utf8(&value[1..]).unwrap_or("non-string").to_string(),
                     );
                 }