Reintroduce deletion of test directories for passing tests.

This now includes a workaround for the problem that we see when deleting
test directories on Windows for tests that memory-map files.

Conflicts:
	community/kernel/src/main/java/org/neo4j/kernel/impl/util/FileUtils.java
Merge pull request #2318 from benbc/2.1-delete-data-for-passing-tests

Reintroduce deletion of test directories for passing tests.