init: prevent the 5min-delay+wipe for dev-mode switch in factory mode
init: prevent the 5min-delay+wipe for dev-mode switch in factory mode

 - early check factory tags and reuse because we will need them twice
 - add extra check so that factory or a scheduled wipe won't enter dev-switch test

BUG=chrome-os-partner:1357
TEST=executed factory_Wipe and then reboot in developer mode

Change-Id: Ia892615a9e83b69d53ad56b4a7366b626a533215

Review URL: http://codereview.chromium.org/3781003

joshfire/chromiumos-platform-init