Add support for HTTPS

[atringham]

At the moment the scheduler, executor and operations only support using http connections. This should be extended to add support for https.
One way is to add a use_https flag (default False) for each of the respective __init__ and set self.scheme to 'http' or 'https' like the following

if use_https:
  self.scheme = 'https'
else:
  self.scheme = 'http'

And the reference this scheme whenever creating a connection to the maser/agent

if self.scheme == "https":
  conn = HTTPSConnection(...)
else:
  conn = HTTPConnection(...)

A change is also needec to resolve the ip to a fqdn for the master/agent in order for the certificates to be validated

I have a patch that does exactly this which I can make PR from if this is an acceptable approach

[ariesdevil]

PR is welcome.

[KieranMDolan]

@atringham was this patch still available for a PR?