Added RadosGW support

Originally https://github.com/crowbar/barclamp-ceph/pull/55

Partially ported from upstream cookbook.

Depends on https://github.com/crowbar/barclamp-keystone/pull/237
No hard-coded /tmp please :-) Either use something like mktemp (I'm sure ruby has that), or put the files in the final destination directory (`nss_dir`) but with names that will make it clear they're only used for conversion.

Btw, that second bit is better because it allows to skip the conversion if the files already exist and are correct (otherwise, this will run every time).

So maybe do something like:

```ruby
directory nss_dir do
 owner node[:apache][:user]
 group node[:apache][:group]
 mode "0755"
 action :create
end

if keystone_node[:keystone][:signing][:token_format] == "PKI"
  file "#{nss_dir}/keystone_pki_ca.pem"
     content keystone_node[:keystone][:pki][:content][:ca]
  end
  bash "convert signing ca certificate to nss db format" do
    code <<-EOH
openssl x509 -in #{nss_dir}/keystone_pki_ca.pem -pubkey | certutil -d #{nss_dir} -A -n ca -t 'TCu,Cu,Tuw' && \
chown #{node[:apache][:user]}:#{node[:apache][:group]} #{nss_dir}/XXXXWHICHFILE?
    end
    subscribes :run, "file[#{nss_dir}/keystone_pki_ca.pem]"
  end

  file "#{nss_dir}/keystone_pki_signing_cert.pem"
     content keystone_node[:keystone][:pki][:content][:signing_cert]
  end
  bash "convert signing certificate to nss db format" do
    code <<-EOH
openssl x509 -in #{nss_dir}/keystone_pki_signing_cert.pem -pubkey | certutil -A -d #{nss_dir} -n signing_cert -t 'P,P,P'' && \
chown #{node[:apache][:user]}:#{node[:apache][:group]} #{nss_dir}/XXXXWHICHFILE?
    end
    subscribes :run, "file[#{nss_dir}/keystone_pki_signing_cert.pem]"
  end
end
```