fix matrix report aggregation bug

We can't use ```endRun```, because endRun is not async. endRun isn't executed right after matrix build finishing, but it's executed according its queue. So, with using jclouds, often endRun is executed, when slave is shutdown already
@pupssman I should it's not good idea, because inside ```startBuild``` I set class variables: ```aggregatedAllureFilePath, tmpResultsDirector```, but inside only method vars.