Somehow this test failed on Windows, because of restoring a "NONE" field
unit to SW_MOD()... apparently the "charborder.odt" test is run first,
and preTest() sees a null SW_MOD() then postTest restores a NONE metric.

Hack around that by calling SwGlobals::ensure() to create SW_MOD().

Change-Id: I6c0cda3aae397071bca16bf0e5d9f8105635550f