Test jclouds location choose reachable address

[bostko]

Used changes from https://github.com/aledsage/brooklyn-server/tree/test-JcloudsLocation-chooseReachableAddress
and https://github.com/bostko/brooklyn-server/tree/test-JcloudsLocation-chooseReachableAddress

[aledsage]

Looks great - love the way you have made JcloudsReachableAddressStubbedTest a true unit test by stubbing out the TemplateBuilder with JcloudsStubTemplateBuilder.

I may take a look at that separately, for how much we hardcode in JcloudsStubTemplateBuilder. And look at using that in more of our tests that don't actually require real responses from the cloud provider!

Merging now.