Allow for multiple users/pws in http_auth secrets

 - cmd.run names property appears to be inconsistent. It seems as if
there is no guarantee that salt executes the commands in the same
order as the template for loop

- explicitly clear auth_file prior to running htpasswd so reliance
on cmd.run order is not necessary
Merge pull request #106 from caktus/fix-saltstack-htpasswd

Allow for multiple users/pws in http_auth secrets