core: don't hit an assert when printing status messages about units with overly long description strings

This essentially reverts one part of d054f0a4d4.

(We might also choose to use proper ellipsation here, but I wasn't sure the
memory allocation this requires wouöld be a good idea here...)

Fixes: #4534

src/core/job.c

@@ -767,8 +767,9 @@ static void job_log_status_message(Unit *u, JobType t, JobResult result) {
         if (!format)
                 return;
 
+        /* The description might be longer than the buffer, but that's OK, we'll just truncate it here */
         DISABLE_WARNING_FORMAT_NONLITERAL;
-        xsprintf(buf, format, unit_description(u));
+        snprintf(buf, sizeof(buf), format, unit_description(u));
         REENABLE_WARNING;
 
         switch (t) {