extra_hosts should be added to services

Add extra_hosts to services

If you have services like selenium_images and you want to test your code with a hostname it is necessary to add specific hostnames for resolution. Currently a service could not be parameterized, but adding the extra_hosts to services would help alot.

If there is another way todo this, I would be glade to here about it.

Proposal

Enhance executors to add extra_hosts params to new services.