Move grizzly tests away from tox.

Since tox is not part of Cloud:OpenStack:.. anymore and SP3 not shipping
it, we user either testrepository or nose.
Don't test oslo.sphinx and oslo.config anymore.

Those will have to move to devel:languages:python, thus simply test in
%check section. pbr is in d:l:p too, because WSME and virtualenvwrapper
%are there too. Lastly, sqlalchemy-migrate in C:OS:M differs from d:l:p,
but not for much longer.
Set '--cpu host' if nested virtualization is supported

Also rename vm_cpus variable to vm_vcpus to avoid confusion with vm_cpu.