Clear Journal before tests

[AndersSahlin]

Before a test is run the journal needs to be cleared. As of now this is done using a hack in ServiceFabricJournalSpec ctor:

ServiceFabric.Journal.ServiceFabricJournal.ClearJournal(Pid, "fabric:/ServiceFabricEventJournalApplication");

[rogeralsing]

cc @clca , the tests needs to clear the test actors journal and snapshot store before each test.
What would be the most idiomatic way of dealing with this. currently, Ive hacked a ClearJournal method onto the ServiceFabricJournal and call this from the tests init method.
This works, but maybe there is a better way of just wiping all data from the current deployment?