The setup() method in CheckLockLocationTest.java calls a private method createFile() to create writable-dir

If the file already exists, createFile() returns true, which I expect would be surprising, especially if 'writable-dir' was a regular file and not a directory due to some external agent.

The reason I looked at this is that I found a two month old file on one of the test systems:

$ pwd
/tmp

$ ls -ld writable-dir writable-dir/*
drwxr-xr-x+ 1 mach5-one None 0 Apr 17 10:49 writable-dir
-rwxr-xr-x 1 mach5-one None 0 Apr 17 10:49 writable-dir/log.log

So for the past two months, subsequent runs of this test have been using an existing directory instead of creating what they need as a precondition.