"Code coverage" badge is broken

[leventov]

Always shows 100%

[asdf2014]

Hi, @leventov . The status icon of Teamcity is also broken. Maybe the administrator should follow
some steps in http://www.mikeobrien.net/blog/setting-up-teamcity-status-badges-with-shields-io to make it correct.

[stale]

This issue has been marked as stale due to 280 days of inactivity. It will be closed in 2 weeks if no further activity occurs. If this issue is still relevant, please simply write any comment. Even if closed, you can still revive the issue at any time or discuss it on the dev@druid.apache.org list. Thank you for your contributions.

[leventov]

Currently, it shows Coverage|unknown

[ccaominh]

This is fixed by #8388