Today's implementation returns 0 even when compared files are
different.
The patch returns 27 (SHELL_NOT_QUAL) in such case to follow
the shell spec.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>