Revert "Devstack should use a prebuilt ramdisk by default"
Revert "Devstack should use a prebuilt ramdisk by default"

This reverts commit 5b752d258a0402abfd7f2511874f42bdf7c77dc1. Due to
devstack-gate only setting IRONIC_BUILD_DEPLOY_RAMDISK=false, this will
prevent IPA source jobs from ever building a new ramdisk.

Change-Id: I3e43c08b7f8e9d41f420b12475c9ce74cb860df9

NaohiroTamura/ironic,NaohiroTamura/ironic,SauloAislan/ironic,SauloAislan/ironic,pshchelo/ironic,openstack/ironic,openstack/ironic,pshchelo/ironic