TrivialFix for flake8 and docs build in tox.ini
TrivialFix for flake8 and docs build in tox.ini

1. exclude "build" in flake8 section.
2. to ensure the old files are not left over when running these
   document builds.

Change-Id: Ia5590b7816b36351559c692eebfecb3c8e6fd1a3

cisco-openstack/tempest,cisco-openstack/tempest,openstack/tempest,Juniper/tempest,masayukig/tempest,masayukig/tempest,Juniper/tempest,openstack/tempest