Made performance improvements to update_bmc.robot.
Made performance improvements to update_bmc.robot.

- Eliminated call to 'Trigger Warm Reset' which contains a 5 min
  sleep.  Replaced with call to obmc_boot_test.py to do
  'OBMC Reboot (off)' which contains "wait fors" rather than sleeps.
- Eliminated unecessary and erroneous call to 'Trigger Warm Reset
  via Reboot'.
- Removed a "Sleep  1 nin" and a "Sleep  7s"
- Eliminated call to 'Set State Interface Version'.

In testing, run time was cut in half.

Change-Id: I9eeb0ad13d6275953ea50c02737d9bbb22d76515
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation