Reset system properties before running the PropertyTests.

Change-Id: I81a8bb4db3fd5b6f7955e2d7416918fa3e9cf97c
Reviewed-on: http://review.couchbase.org/28786
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>