Add agent_ipmitool support

This patch enables to use the agent_ipmitool deploy driver to
deploy the ironic on real hardware, instead of virtual machine.

It also append the deploy driver name to the kernel/ramdisk
path, so that if developer switch the deploy driver after
./unstack.sh, devstack will use the correct kernel/ramdisk.

Change-Id: Iac0415f6895d037c876e137aa4f2bf2990eb47c5
Merge "Add agent_ipmitool support"