Change group_replication_exit_state_action default option to READ_ONLY

In MySQL 8.0.16, the Group Replication plugin variable group_replication_exit_state_action default value has been changed to READ_ONLY. The group_replication_exit_state_action plugin variable was introduced in MySQL 8.0.12 to allow the user to configure how Group Replication behaves when a server instance leaves the group unintentionally. The group_replication_exit_state_action has following two values: ABORT_SERVER: Continue Reading

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