Bug-4957 Cluster Role change fix

Bug-4957 Cluster Role change fix

* TxManager shutdown fail has to clean DS (put empty Node)
* DeviceCtx onRoleChange needs call Device Initialization
  functionality but we need to know when we are able to
  put fresh data in to Oper DS and when we could jump
  write functionality
* DeviceCtx contract change for method OnClusterRoleChange

Note: Cluster Master to Slave change could finish during
initialization phase or TxManager could fail in submitting
last transaction state. So we needs a marker for "something
unexpected is happend" and we have to put fresh data to
Operational DataStore

Change-Id: I18e8c0d75e2e5cf195d9a98c1e096fb5517fab72
Signed-off-by: Jozef Bacigal <jbacigal@cisco.com>
Signed-off-by: Vaclav Demcak <vdemcak@cisco.com>