fixes #2633 - enable generate_token rake task to run from elsewhere

scratch build: https://koji.katello.org/koji/taskinfo?taskID=39097

<pre>
[root@rhel6b ~]# rpm -ivh "http://koji.katello.org/koji/getfile?taskID=39097&name=foreman-1.2.9999-4.el6.noarch.rpm" "http://koji.katello.org/koji/getfile?taskID=39097&name=foreman-sqlite-1.2.9999-4.el6.noarch.rpm"
Retrieving http://koji.katello.org/koji/getfile?taskID=39097&name=foreman-1.2.9999-4.el6.noarch.rpm
Retrieving http://koji.katello.org/koji/getfile?taskID=39097&name=foreman-sqlite-1.2.9999-4.el6.noarch.rpm
Preparing...                ########################################### [100%]
   1:foreman                ########################################### [ 50%]
   2:foreman-sqlite         ########################################### [100%]
[root@rhel6b ~]# ll ~foreman/config/initializers/local_secret_token.rb
-rw-r-----. 1 root foreman 570 Jun 10 17:04 /usr/share/foreman/config/initializers/local_secret_token.rb
</pre>