master: Forbid changing personality from and to cluster-managed

Forbid changing personality from non ha-cluster-managed to
ha-cluster-managed and the other way around.

Change-Id: I7dbf8291a155bb70e0de23dc3a8dda1a16ccb7dd
master,admin: Add a possibility to remotly stop master server

This is option stop-master-without-saving-metadata in lizardfs-admin.

Change-Id: I7bad1b20f0350d8ebf413413c8c4add07d96da4e