prototypes: bifrost: Fix Ironic drivers for VMs

prototypes: bifrost: Fix Ironic drivers for VMs

Commit d8235c3c97f4("Set database pool_size in ironic.conf and
inspector.conf templates") added a copy of the ironic.conf.j2
template file to workaround an upstream bug but it also changed
the default ironic drivers leading to broken introspection. We use
virtual BMC for controlling the VMs and this expects ipmi ironic
drivers so we fix that.

Change-Id: Ibb2cc58738ec1693e136bdce7335cd1b861ec613
Fixes: d8235c3c97f4("Set database pool_size in ironic.conf and inspector.conf templates")
Signed-off-by: Markos Chandras <mchandras@suse.de>