Add methods to ipmitool driver

This commit adds two methods to the vendor interface for the
ipmitool driver:

* send_raw: this is used to send arbitrary bytes to a BMC. One
  example of a use case for this is: many BMCs fail in strange ways
  when 'chassis bootdev disk' is sent without first sending a
  certain sequence of bytes. This is common enough that pyghmi
  even does this by default. Takes one parameter, 'raw_bytes',
  which is the string representation of which bytes should be
  sent. For example: '0x00 0x01'.

* bmc_reset: used to reset a BMC. A cold or warm reset can be
  selected by setting the warm parameter to False (cold) or True
  (warm). Defaults to warm.

Closes-Bug: 1340199
Change-Id: I508eabae7428daea29d749bb2aa9fc9c5a357e8c
Merge "Add methods to ipmitool driver"