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

Since commit 06c1c6e 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 nova.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).