Fix Git repository plugin test failures on Windows

Using the same checkout directory for both tests was resulting in test
failure on my Windows 7 64-bit machine.  My assumption is that Windows
is doing some wonky things under the hood when files are deleted that
cause the 'put' test to fail.

Signed-off-by: Sean Bright <sean@malleable.com>
Merge pull request #891 from seanbright/fix-git-repo-plugin-testcases

Fix Git repository plugin test failures on Windows