journal probe: filter LOG_EMERG logs as well

I omitted log level 0 from the filter, so add it here.

Signed-off-by: Patrick McCarty <[email protected]>

src/probes/journal.c

@@ -229,7 +229,8 @@ static bool add_filters(sd_journal *journal)
         MATCH(data);
         free(data);
         AND;
-        // The three highest log levels, all indicating errors
+        // The four highest log levels, all indicating errors
+        MATCH("PRIORITY=0");
         MATCH("PRIORITY=1");
         MATCH("PRIORITY=2");
         MATCH("PRIORITY=3");