Replace rm -rf requirements.txt step with proper rpm macro

[chkumar246]

In RDO packaging, we use rm -rf requirements.txt/test-requirements.txt in order to
avoid python package installation from pip during rpm package building process.
Since from Pike release, we have to replace this step with rpm macro %py_req_cleanup.

How to reproduce:

1. Clone openstack-nova spec file git clone https://github.com/rdo-packages/nova-distgit
2. Go to nova-distgit and open openstack-nova.spec in editor.
3. You can find rm -rf {test-,}requirements.txt tools/{pip,test}-requires under %prep section
   in spec file.

How to fix:

1. Replace ** rm -rf {test-,}requirements.txt tools/{pip,test}-requires ** with %py_req_cleanup
2. Add BuildRequires: openstack-macros just below description section of main package.
3. Add the changes file, commit it and send a Gerrit review.

Below is the list of packages which need same fixes:

• openstack-nova
• openstack-glance
• openstack-cinder
• openstack-swift
• openstack-neutron
• openstack-keystone

Mentor: chandankumar
Note: Pick one of the package and comment in the comment box with review link.

[OGtrilliams]

Trying to update cinder, but not sure if I did it right: https://review.rdoproject.org/r/#/c/7637/

[OGtrilliams]

Did glance, too https://review.rdoproject.org/r/#/c/7685/

[snecklifter]

Again, I'm sure there are more so a good grepping of spec files needs doing.