Update server_mode.rst with shell usage example

[tomers]

Suggest to create a aws alias which contains the --endpoint-url http://localhost:5000 command-line option

[bblommers]

It does make sense to have a CLI example here, but I think that we should just show that the parameter exists. E.g.:

aws ec2 describe-instances --endpoint-url http://localhost:5000

If a user wants to create an alias for that, that is up to them.