Avoid creating a new 'err' variable in the 'if'-branch, shadowing the one
in the outer scope.

Any error from subsequent 'cloud, err = GetCloudProvider()' was not propagated
to 'err' variable in the outer scope and thus errors were never returned from
this function.

This is hard to debug error on OpenStack, when content of --cloud-config=
file is wrong or connection to OpenStack fails. Such error is never logged
and Kubernetes thinks everything is OK.