It was decided (http://cactuscode.org/pipermail/developers/2010-September/006087.html) that the built-in CartGrid3D symmetries are deprecated and will not work with the Mercurial version of Carpet. Any test cases that use Grid::domain != "full" should be modified to use ReflectionSymmetry instead.
In general, this should be possible without regenerating the test output. However, for the case of AHFinderDirect, the horizon finder actually uses a different internal multipatch grid structure if it detects that a CartGrid3D symmetry is being used. This means that the horizon shapes and quantities are different at the level of numerical error with ReflectionSymmetry. I propose to convert the tests to use ReflectionSymmetry and regenerate the test data (the grid function phi is the same with the new symmetry thorn, it's only the horizons which are different). The failing tests are related to checkpoint and recovery, and are not designed to test the symmetry mechanism.