MdeModulePkg/Variable/RuntimeDxe: permit MorLock deletion for passthru req

MdeModulePkg/Variable/RuntimeDxe: permit MorLock deletion for passthru req

The SetMorLockVariable() function sets "mMorLockPassThru" to TRUE
temporarily, so that it can set the MOR Control Lock variable to
well-formed values without permission checks.

In the next patch, we'll need the same override for deleting the MOR
Control Lock variable; hence obey "mMorLockPassThru" in the deletion
branch of SetVariableCheckHandlerMorLock() as well.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ladi Prosek <lprosek@redhat.com>
Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Tested-by: Ladi Prosek <lprosek@redhat.com>