259: Test xfs fs creation with fs size close to 4 TB

259: Test xfs fs creation with fs size close to 4 TB

mkfs.xfs failed to create xfs filesystems with 4 TB minus few bytes due
to round up error in mkfs.xfs code.
This test case is a regression test for the fs creation problem.

I've tested the test case with mkfs.xfs patch (in the form posted by
Eric Sandeen) and the test passed (and therefore the patch fixed the
issue for me).

I'm not sure whether bash guarantees at least 64-bit precision
values in its arithmetic operations.  Therefore the values are
computed in advance.

Signed-off-by: Boris Ranto <branto@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>