add rbd keyring name to secret.xml template

With Change-Id: I7342ec1337cf86c0e4bc66b1788e65c53b2878ce
a parameter for configuring the rbd keyring name was introduced.
This parameter should be used in the secrets file also.

Change-Id: I9da148f7f2e940f1d4dec73e1df6f283028bcca1