Refine the logic, based on the varstore name and guid to find a varstore, old logic only base on name to find it.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>



git-svn-id: https://edk2-buildtools.svn.sourceforge.net/svnroot/edk2-buildtools/trunk/BaseTools@2568 c2973edb-eda0-4c78-bc6a-9341b269661f