Additional options for keystone-paste.ini

* This change allows further flexibility with
handling keystone-paste.ini
* We now support pulling from a local file
(redhat use case), pulling from a remote file,
and finally template functionality (default)
* We support a misc_paste chef attribute to add
custom lines to the keystone-paste.ini when using
the templated version

Change-Id: I9a9adf3fd63df7a36deea274aac51ecd08335bfa