Ensure that api-paste.ini does not contain the auth_token

Since commit 444211b removed the api-paste.ini template from chef, systems
which already had it installed by chef would keep the old version because it
was modified outside of rpm. But these files contained the auth_token
middleware configuration which would conflict with the one from neutron.conf.

This commit fixes that problem by making sure to overwrite api-paste.ini
with a vanilla file from the git repository (current stable/icehouse).
Merge pull request #147 from vuntz/reset-api-paste

Ensure that api-paste.ini does not contain the auth_token