Recreate initramfs within loopback image

dracut has a loop [1] where it probes top-level directories, tries to
find what block device they are on, then determines the file-system of
that block device.  It then puts those file-system modules into the
initramfs for boot.

Since we install the kernel package during the chroot phase, / there
is not a block device and thus this loop matches nothing and we end up
with no file-system modules in the initramfs.  This results in a very
annoying silent boot hang.

By moving re-generation of dracut into finalise.d phase, we run inside
the final image where / is the loop-device; the root file-system gets
detected correctly and the ext4 module is included correctly.

[1] http://git.kernel.org/cgit/boot/dracut/dracut.git/tree/dracut.sh?h=RHEL-7#n1041

Change-Id: Iaf2a1e8470f642bfaaaad3f9b7f26cfc8cc445c9
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

elements/yum-minimal/finalise.d/55-dracut-recreate

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# Recreate the initramfs within the loop device so everything gets
+# picked up correctly.
+
+if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+dracut --regenerate-all --force --verbose