Disable IPMI timeout before setting boot device

IPMI specs indicate that unless you explicitly disable it, there's a 60
second timeout after setting boot device: if you don't reboot in that
time the request in cancelled. Additionally, there's some hardware that
behaves very badly when these bytes aren't sent.

The timeout is already disabled by default in the ipminative / pyghmi
driver.

Change-Id: Ia1aa8814e2f48b32fa03f4e796b4c67d4f8c3fe4
Closes-bug: 1390667
Merge "Disable IPMI timeout before setting boot device"