[core] Make the wait timeout truly global

The Rackspace helper changed the Fog.timeout global for all live tests
so the core test which expected "600" failed since it was now "2000"

Since it is a global setting it has been moved to the global test helper

It can now also be controlled by the FOG_TEST_TIMEOUT env variable.
Merge pull request #2690 from fog/make_timeout_change_global

[core] Make the wait timeout truly global