Vserver create API was failing since 'retention_period' is no longer supported in POST (create) call. Fixed it by moving 'retention_period' setting to PATCH (update) call. Closes-bug: #2111918 Change-Id: I6d9fcd5a70673f0007b73d5c8e7536b118567088 Signed-off-by: Kiran Pawar <kinpaa@gmail.com>