Mark ironic-discoverd-ramdisk as deprecated in favor of ironic-agent
Mark ironic-discoverd-ramdisk as deprecated in favor of ironic-agent

Also fix no longer correct parts of its README.

Change-Id: I00cbe5b4f65f9909ae63b7eb4bbac0ba82c145d1

takahashinobuyuki/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,zioproto/diskimage-builder,takahashinobuyuki/diskimage-builder,switch-ch/diskimage-builder,zioproto/diskimage-builder,openstack/diskimage-builder,switch-ch/diskimage-builder,openstack/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder