Modified the client_alive_interval default to suggested value from cis benchmark.
Modified the client_alive_interval default to suggested value from cis benchmark.

While this cookbook isn't specific (and shouldn't be specific) to CIS Benchmarks, it's helpful as a
baseline to set the default behaviors to the recommended value. Folks can override to 600 if needed.

Signed-off-by: Jennifer Davis <d4e7f8d2b5f99113b004038410765a733ae70470@gmail.com>

hardening-io/chef-ssh-hardening,hardening-io/chef-ssh-hardening,dev-sec/chef-ssh-hardening,dev-sec/chef-ssh-hardening