Remove bashism from monit nodejs template

https://github.com/aws/opsworks-cookbooks/blob/release-chef-11.10/opsworks_nodejs/templates/default/node_web_app.monitrc.erb#L2 - this uses `source` to set up the environment but actually `dash` is a default shell in Ubuntu and it does not support the command: https://wiki.ubuntu.com/DashAsBinSh#source