metricAdapter startup error：“unknown flag: --alsologtostderr", and also "--v"

[abrahamhwj]

          metricAdapter startup error, indicating “unknown flag: --alsologtostderr", and also "--v"

Who can help answer it, thx very much：

1. What is the reason for this problem？
2. What do these two flags do?
3. What's the problem if cancel them?

Originally posted by @abrahamhwj in #910 (comment)