crosutils: clean up make_factory_package
crosutils: clean up make_factory_package

This is part of clean-up in factory related scripts.

Calling mk_memento_images does not need sudo, and some pushd can be removed
because most operations take full path now.

BUG=chromium-os:15050
TEST=./make_factory_package --release RECOVERY --factory FACTORY

Change-Id: I323c9abbc4a98b22736c755669f8ecd18b05cfd5
Reviewed-on: http://gerrit.chromium.org/gerrit/5964
Reviewed-by: Nick Sanders <f4566bb3c90c0bf5fa0906b296b1da45051a62ee@chromium.org>
Tested-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>

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