Do not delete src_image if --notest_mod is set.
Do not delete src_image if --notest_mod is set.

TEST=From an already built image dir, ran archive_build with --notest_mod
set and verified the image had chromiumos_base_image.bin and chromiumos_image.bin.

Review URL: http://codereview.chromium.org/2111015

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