Part(3/3) - If verified rootfs is enabled, prompt user to use /usr/local as root.
Part(3/3) - If verified rootfs is enabled, prompt user to use /usr/local as root.

Change-Id: I47cb37d4f5766b49e3805faee838a8e98d8b96d5

BUG=chromium-os:8886
TEST=Tested with gmerging packing that rootfs.

Review URL: http://codereview.chromium.org/5683004

mgireesh05/dev-util,marineam/coreos-dev-util,coreos/dev-util,coreos/dev-util,mgireesh05/dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util