* Enable http2 by default
* Disable server_tokens by default

This reverts commit 79e9bce0.

THis would break existing setups. Will revisit later on.

Ref: https://github.com/jitsi/docker-jitsi-meet/issues/433

This partially reverts
https://github.com/jitsi/docker-jitsi-meet/commit/5e6faced4ff7724b65d608f6fe93fabe70743efd

It was unnecessary, and created lot of trouble.

Also check if they are not provided at sstartup time and fail to start
in that case.

Ref:
https://github.com/jitsi/jitsi-meet/commit/06641a7dd6baff6f854591ad2f05ff18a9221c62

Otherwise conferene.isSIPCallingSupported() will return true.