Refactor: Move post method to APIValidationTestCase base class
Refactor: Move post method to APIValidationTestCase base class

There are 25 occurences in the code where post method is
defined in the setUp method of the inherited classes.

This patch is intended to move the post method to the
APIValidationTestCase base class to reduce size of code.

TrivialFix
Co-author-by: Dinesh Bhor <0ae1e1a73461bc9ec98a3f74b0ee8a78b85bea79@nttdata.com>
Change-Id: I509e6e9dbc52f9715276247d8e8c5bb7683d2254

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