There's a bug in the installer of RHEL-6 which results in one or more
invalid records added to zipl.conf if kernel-kdump package was part of
initial installation.  If these invalid records persist, system may not
be able to boot into upgraded RHEL-7.

It is recommended to review the zipl.conf file and remove the invalid
records manually. Otherwise, redhat-upgrade-tool will attempt to remove
them.
