Clustering: Use generated serialVersionUID for Serializable messages

https://git.opendaylight.org/gerrit/#/c/12649/ changed several Serializable messages classes to set serialVersionUID to 1. However this will break backwards compatibility when attempting to de-serialized messages from a prior Helium version since no serialVersionUID was not previously set.

Instead of setting it to 1, we need to set it to a generated value which should match the value generated at runtime for a previous serialized version of the class.