Add ulimit flag to Flow docker container

For the upcoming flow mainnet spork on 22nd Feb (see announcement), please also add this additional ulimit parameter to the docker configuration for all node types.

--ulimit nofile=8192

Example of the docker config with the flag is here.

This higher ulimit is required to address the networking issue that was observed earlier, where some nodes failed to connect to other nodes. More on the issue here.

Thank you,
Flow Team.