EventJournalProcessor or DefinitionMergeService must implement mechanism to reset runtime configuration model

Currently, EventJournalProcessor gets the current runtime configuration model as one of the first instructions in EventJournalProcessor#processEvents:

this.currentModel = configurationService.getRuntimeConfigurationModel();

This currentModel is passed into DefinitionMergeService, which modifies that model in for instance DefinitionMergeService#mergeConfigDefinitionNode:

new ConfigurationTreeBuilder(model.getConfigurationRootNode())
    .markNodeAsDeletedBy(incomingConfigNode, 
    deleteDef).pruneDeletedItems(incomingConfigNode);

The problem is that in case of exceptions in DefinitionMergeService the changes in the model are not reset.

While fixing this, also look into the following code in EventJournalProcessor#checkAddEventPath:

final ConfigurationItemCategory category = autoExportConfig.getCategoryForItem(eventPath, propertyPath,
    configurationService.getRuntimeConfigurationModel());