e2edev should test exchange https port

[bmpotter]

In the test/Makefile line that sets DOCKER_EXCH it should be changed to:

DOCKER_EXCH ?= https://exchange-api:8080/v1

so that the tests are exercising the https port of the exchange. But this means that everywhere that variable is used has to make sure that it also sends the cert in the request.

The only exception to this is CSS can't use the exchange https port until issue https://github.com/open-horizon/anax/issues/2628 is fixed.