Replace key manager with Castellan

Because key manager code is duplicated across several projects, a key
manager interface was moved into its own library. This goes back to
replace the old code with the new library.

Implements: blueprint use-castellan-key-manager
Change-Id: Ief8885bb4ca8d62b03cf1a52c25dd0e62c835bfe

cinder/config/cinder-config-generator.conf

@@ -1,6 +1,7 @@
 [DEFAULT]
 output_file = etc/cinder/cinder.conf.sample
 wrap_width = 79
+namespace = castellan.config
 namespace = cinder
 namespace = keystonemiddleware.auth_token
 namespace = oslo.config