test: bump the container spawn timeout to 60s

As 30s might be not enough on busy systems (and we already bumped the
reboot timeout from 30s to 60s for this reason).

test/test-shutdown.py

@@ -18,7 +18,7 @@ def run(args):
     logger.info("spawning test")
     console = pexpect.spawn(args.command, args.arg, env={
             "TERM": "linux",
-        }, encoding='utf-8', timeout=30)
+        }, encoding='utf-8', timeout=60)
 
     if args.verbose:
         console.logfile = sys.stdout