Pass ipa-driver-name to agent ramdisk

This commit adds the change to pass ipa-driver-name to
agent ramdisk.  This enables agent ramdisk to do
vendor-passthru lookup on the actual driver instead of
the default 'agent_ipmitool' driver.

Change-Id: I750097dc24e11b44d4ed6d7c314cb8fb470dfcb0
Closes-bug: #1371505
Merge "Pass ipa-driver-name to agent ramdisk"