Allow nss db files to be created for keystone integration

[andymcc]

Specify keystone signing/ca.pem file and have radosgw recipe automatically convert these.
Only run if both ca/signing_cert and nss db path are specified.

[andymcc]

Added a check so the execute block won't run everytime

[hufman]

Would this functionality be better suited in a wrapper cookbook? You will need to set the attributes for keystone_ca and keystone_signing, and the rest of the functionality is mostly generic. The main tie into Ceph is the node['ceph']['config']['rgw']['nss db path'], which can be set anywhere.

The attribute that sets the process_owner can't be determined automatically. For example, radosgw currently runs as root on Debian servers. It shouldn't be guessed from apache attributes, because that will fail if the apache cookbook is not loaded. That would also prevent the eventual inclusion of alternate companion webservers.
This change would also not support updating the key in the nss db if it changes for any reason.