logs.py: don't print (unchanged) lines with --no-log unless DEBUG.

This accidentally made output look different with --no-log vs with
normal redo-log output, because redo-log has a -u option while plain
redo does not.

(This is on purpose.  When running redo, you only want to see the things
that actually happened, so it never passes -u to the auto-launched
redo-log instance.  But when reviewing logs later, you might want to
look at the past logs from building a component that was unchanged in
the most recent run.)

redo/logs.py

@@ -71,7 +71,8 @@ class PrettyLog(object):
             kind, pid, _ = words[0:3]
             pid = int(pid)
             if kind == 'unchanged':
-                self._pretty(pid, '', '%s (unchanged)' % text)
+                if env.v.LOG or env.v.DEBUG:
+                    self._pretty(pid, '', '%s (unchanged)' % text)
             elif kind == 'check':
                 self._pretty(pid, GREEN, '(%s)' % text)
             elif kind == 'do':