Check BMC availability in ipmitool 'validate' method

Check that BMC is accessible with provided IPMI credentials added
to 'validate' method of ipmitool driver, simple command 'mc guid'
used.

Partial-Bug: #1255648
Change-Id: I8942163a80e2d76784fa973a349d6fdd6f0b8110
Merge "Check BMC availability in ipmitool 'validate' method"