* Move some more atomic values under Channels
The following fields were moved:
```
asymmetricSigningKey atomic.Value
clientConfig atomic.Value
clientConfigHash atomic.Value
limitedClientConfig atomic.Value
```
And also moved the initialization order from NewServer
to Channels.Start to better reflect the order of things.
Removed AsymmetricSigningKey from ConfigService
as it was no longer used.
Removed calling regenerateClientConfig during startup explicitly
because it was anyways called from ensureAsymmetricSigningKey.
https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4?c=87df1e15-588e-49ff-8bd1-ffa9651b8c82
```release-note
NONE
```
* Fix lint error
```release-note
NONE
```
* Consistent license message for all the go files
* Fixing the last set of unconsistencies with the license headers
* Addressing PR review comments
* Fixing busy.go and busy_test.go license header
