Use host information passed while starting service

While starting the heat engine service, the host parameter value
being passed to EngineService should be used instead of referring
the conf.
Similarly in the case of EngineListener.

Change-Id: I365f7e21637776d2e7da7685790758f3dcd06989
Improve error for custom resource

Improve error for case when custom template resource specified via http
or https url. Same behaviour is presented for python-heatclent.

Change-Id: I05c6bad3e6a52ca041fd8a51849ff4e6af23baed
Closes-Bug: #1376656
Merge "Improve error for custom resource"
Merge "Use host information passed while starting service"