Remove code that produces warning in modern Python
Remove code that produces warning in modern Python

When running py27 tests, you will see a bunch of the following
warnings:

BaseException.message has been deprecated as of Python 2.6

Because of some old code in the OpenStackApiException base class that
was setting the message attribute of the base class. This code isn't
necessary.

Change-Id: I24357d3069f653a707f15abb34d9d2546c3ee044

gooddata/openstack-nova,jianghuaw/nova,Juniper/nova,klmitch/nova,phenoxim/nova,rahulunair/nova,mahak/nova,mikalstill/nova,vmturbo/nova,gooddata/openstack-nova,Juniper/nova,mikalstill/nova,Juniper/nova,jianghuaw/nova,klmitch/nova,mikalstill/nova,vmturbo/nova,rahulunair/nova,openstack/nova,openstack/nova,vmturbo/nova,gooddata/openstack-nova,klmitch/nova,klmitch/nova,rahulunair/nova,jianghuaw/nova,openstack/nova,gooddata/openstack-nova,mahak/nova,vmturbo/nova,phenoxim/nova,jianghuaw/nova,Juniper/nova,mahak/nova