Solidfire: Fix pylint errors for class decorators
Solidfire: Fix pylint errors for class decorators

A couple decorators used within the Solidfire driver were defined
as class methods rather than their own functions. This results in
the pylint errors:

"Method should have \"self\" as first argument"

Since these do not need access to self, there is no reason they
should be class methods. This moves them out to be their own
functions.

Change-Id: Ia4da36987783fb0e3f2c44857a3cf9d586c5e769

openstack/cinder,openstack/cinder,mahak/cinder,mahak/cinder