crosutils: fix factory install shim when booting with legacy EFI firmware
crosutils: fix factory install shim when booting with legacy EFI firmware

Verified boot is not supported yet for USB+EFI boot, which is the case
of factory install shim.  We need to select normal boot in legacy boot
loaders when building factory install shim.

BUG=chrome-os-partner:6358
TEST=build_image --factory_install
     # boots successfully under ZGB H2O firmware

Change-Id: Ic4645a1766514bf7e0c31f8a4df21452bf195705
Reviewed-on: http://gerrit.chromium.org/gerrit/10013
Tested-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>
Reviewed-by: Richard Barnette <9e7d66387742bf40b0d2548ef2b93e7c522ca0eb@chromium.org>
Reviewed-by: Nick Sanders <f4566bb3c90c0bf5fa0906b296b1da45051a62ee@chromium.org>

zhang0137/scripts,nicescale/scripts,mischief/scripts,vmware/coreos-scripts,mjg59/scripts,glevand/coreos--scripts,endocode/scripts,mjg59/scripts,crawford/scripts,bcwaldon/coreos-scripts,andrejro/coreos--scripts,fivethreeo/scripts,fivethreeo/scripts,zhang0137/scripts,andrejro/coreos--scripts,trnubo/scripts,BugRoger/scripts,bcwaldon/coreos-scripts,sigma/coreos-scripts,marineam/coreos-scripts,gtank/scripts,mischief/scripts,smilart/scripts,vmware/coreos-scripts,mischief/scripts,crawford/scripts,sigma/coreos-scripts,bcwaldon/coreos-scripts,endocode/scripts,fivethreeo/scripts,zhang0137/scripts,BugRoger/scripts,marineam/coreos-scripts,smilart/scripts,coreos/scripts,gtank/scripts,nicescale/scripts,gtank/scripts,andrejro/coreos--scripts,crawford/scripts,trnubo/scripts,marineam/coreos-scripts,sigma/coreos-scripts,trnubo/scripts,smilart/scripts,endocode/scripts,vmware/coreos-scripts,mjg59/scripts,glevand/coreos--scripts,BugRoger/scripts,coreos/scripts,nicescale/scripts