Fix .gitignore for .tox and .testrepository

The entries for tox and testrepository weren't
working with `git clean -df` so this updates them
to match what's in nova's .gitignore. Testing
manually shows this doesn't blast those directories
when running git clean.

Change-Id: Iba569afabea748369f76351bf5521ca1c0fdce0c
Closes-Bug: #1423983

.gitignore

@@ -1,7 +1,7 @@
 AUTHORS
 ChangeLog
-.tox/*
-.testrepository/*
+.tox
+.testrepository/
 *.pyc
 *data/*
 *build/*