Write details into a separate .dat file in case of Galera node auto-eviction

Galera provides a way to automatically remove a node from cluster if other nodes seem to have problems with it (like unusuallydelayed response times), see https://galeracluster.com/library/documentation/auto-eviction.html.

It would be useful to get the eviction status written to a file like gvwstate.dat in order to easily identify when a node was evicted without going through the logs. This would help to find out easier if proper analysis is needed instead of just restarting the node blindly in a hope it works majically.