[BUGFIX] Relax FormViewHelper unit test
With the previous change (I944ad1389092d97000acc89d591a0d05b887232d)
the Fluid unit tests fail in some circumstances due to a bug in the
``parse_url()`` PHP function (https://bugs.php.net/bug.php?id=52923).
This change works around this issue by relaxing the respective test.
Note: This only addresses the master branch. In the other release
branches the fix will be included into the original change.