logs: use %o to format error

otherwise, they are printed as multi-line and this messes up tail+date formatting

src/janitor.js

@@ -18,9 +18,9 @@ async function cleanupTokens() {
     debug('Cleaning up expired tokens');
 
     const [error, result] = await safe(tokens.delExpired());
-    if (error) return debug('cleanupTokens: error removing expired tokens', error);
+    if (error) return debug('cleanupTokens: error removing expired tokens. %o', error);
 
-    debug(`Cleaned up ${result} expired tokens`,);
+    debug(`Cleaned up ${result} expired tokens`);
 }
 
 async function cleanupTmpVolume(containerInfo) {