[Docker] joynr-base Dockerfile uses optional proxy host and port arguments
[Docker] joynr-base Dockerfile uses optional proxy host and port arguments

* also rearranged some statements since proxy configuration must be
  setup prior to first remote call

Change-Id: I08e0803da2d4e33426f28ed904eb6a627e6f47d6

bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr