Re-enable URLHandleTest

See https://trello.com/c/IqXLdRjl/75-fix-test-url-in-urlhandletest.  All builds should be green, and ```URLHandleTest``` should appear in the reports in ```components/formats-common/test-output``` when ```ant test``` is run from ```components/formats-common```.
Windows hasn't (yet) compained about the `\` but has about the `C:` -- https://ci.openmicroscopy.org/view/Failing/job/BIOFORMATS-5.1-merge-build-win/345/testReport/loci.common.utests/URLHandleTest/_BeforeMethod_setup/