Upgrade nats-server to >2.1.9

[rogeriopeixotocx]

There's a critical vulnerability CVE-2020-26892 in the dependency nats-server v2.1.2.

Can anyone update the dependency to a version greater than 2.1.9?

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26892

[rogeriopeixotocx]

I see a pull request to do it #1082

please fix the tests

[sagikazarmark]

I believe this is done. There is also #1101 to reduce the dependence on the nats server from go-kit.