Avoid overriding predefined otp_column value when initializing resource

Currently there is no way of predefining a value for the otp_column as it is being overridden by the before_create callback.

Use case: admin user that creates other users, can only have access to the code when creating those users. If the code is generated on an after_create callback, it has to be visible on other views (besides resource.new) in order to have access to the code.

NOTE: Did not know if gem should add attr_accessible for otp_column by default or if it has to be added manually on the resource with has_one_time_password.