Restore original value of CAM's boot delay and instead extend root
mount's delay to 30 seconds from the default 3 seconds, in the hope
to address USB boot problem.

Note that we were not able to reproduce the problem at lab so we
need the community to help testing this.

(cherry picked from commit a28a2a6b4c4f756290f4d65b67d815c9d27d88e6)