TCK tests for shareable nodes assume moving shareable nodes is not supported

There are two tests in ShareableNodeTest that assume that an implementation does not support moving shareable nodes. This is inconsistent with what is required by JSR-283.

1) testMoveShareableNode assumes that the implementation does not support moving nodes that are 'mix:shareable' (even when they are not yet shared) using Workspace.move(...).
2) testTransientMoveShareableNode makes a similar assumption to #1, except that it uses the Session.move(...) operation.

Both of these test should be changed to allow an implementation to either not support the operation (e.g., Jackrabbit) or to properly check the results.