[rackspace] A test to reveal a bug in server.create
[rackspace] Fixes issue #2187 Compute.servers.bootstrap mutates the :networks option

Server.create modified the options it got. Most modifications were
reusable in succeeding invocations but mapping the :network ids
to json was not. It is safer to use a copy for all the values anyway
Merge pull request #2192 from reynders/fix_2187

Fix issue #2187