run --mode=devstartup unconditionally if we booted developer firmware

Change-Id: Ice7d5343b50343f4cb0f323929c4e53132638cc8

BUG=none
TEST=boot system with developer mode firmware

Review URL: http://codereview.chromium.org/6745022
(cherry picked from commit df8cdb52f39c41d65bb1f108241ae2940a73a643)

Review URL: http://codereview.chromium.org/6770022
1 file changed