Early return when the "BootOrder" variable doesn't exist to avoid SetVariable() return EFI_NOT_FOUND.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15489 6f19259b-4bc3-4df7-8a09-765794883524
Config Access Protocol return value not follow spec, update code to follow it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Gao, Liming <liming,gao@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15490 6f19259b-4bc3-4df7-8a09-765794883524
Merge branch 'master' of https://github.com/tianocore/edk2