Use 'id' instead of 'whoami' to determine user identity 'whoami' is missing in some environment such as initramfs. Let's use 'id' instead. BUG=chrome-os-partner:17368 TEST=Factory install. Change-Id: Ibdbcd58f7759944616a3e08c8e5fded7ceeeca33 Signed-off-by: Vic Yang <[email protected]> Reviewed-on: https://gerrit.chromium.org/gerrit/41919 Reviewed-by: Hung-Te Lin <[email protected]>