UnitTestFrameworkPkg/UnitTestLib: Correct dereferred pointer

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2609



SavedState is not sticky, copied pointer update will not change source
pointer

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Signed-off-by: Guomin Jiang <guomin.jiang@intel.com>
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>