BUG: reduce the size of test driver

The list of files for the test driver was not cleared after a new
number was created. The cased each test driver to have all prior
tests. Not the drivers are correctly split.

Change-Id: Ice249a980c49e49f793ba69ee05f6949e113fb96
Merge topic 'FixTestDriverSplit' into next

f1a2286 BUG: reduce the size of test driver