If we don't do this, then a number of modules will be missing from
the image's ramdisk. One example is the multipath module - this
has a dependency on device-mapper-multipath, which is installed as
part of the image build. However, by default the ramdisk is not
rebuilt after the package is installed so it never takes effect.
This is the particular case I'm trying to address because it
prevents deploying to diskless systems that use iscsi targets as
their root disks. With this change, the necessary modules for such
a deployment will be in the ramdisk.
Change-Id: I3c6a94070ebba39896d00250a14b655969406459
a4e59c7aea