Why installation of a new kernel package on Red Hat Enterprise Linux 6 (s390x) system does not update the value of DEFAULTKERNEL in /etc/sysconfig/kernel file ?

Issue

• Installation of a new kernel package on Red Hat Enterprise Linux 6 (s390x) system does not update the value of DEFAULTKERNEL in /etc/sysconfig/kernel file.

• Installation of a new kernel package on Red Hat Enterprise Linux 6 (s390x) system does not update the value of default in /etc/zipl.conf file. This is /etc/zipl.conf after running "yum update kernel":

[defaultboot]
timeout=5
default=linux-2.6.32-358.18.1.el6.s390x
target=/boot/
[2.6.32-431.11.2.el6.s390x]
        image=/boot/vmlinuz-2.6.32-431.11.2.el6.s390x
        parameters="root=/dev/disk/by-path/ccw-0.0.0201-part1 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD  KEYTABLE=us SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_DASD=0.0.0102 rd_NO_LVM rd_DASD=0.0.0201 rd_NO_DM"
        ramdisk=/boot/initramfs-2.6.32-431.11.2.el6.s390x.img
[linux-2.6.32-358.18.1.el6.s390x]
        image=/boot/vmlinuz-2.6.32-358.18.1.el6.s390x
        ramdisk=/boot/initramfs-2.6.32-358.18.1.el6.s390x.img
        parameters="root=/dev/disk/by-path/ccw-0.0.0201-part1 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD  KEYTABLE=us SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_DASD=0.0.0102 rd_NO_LVM rd_DASD=0.0.0201 rd_NO_DM"
[linux-kdump-2.6.32-358.18.1.el6.s390x.kdump]
        image=/boot/vmlinuz-2.6.32-358.18.1.el6.s390x.kdump
        parameters="root=/dev/disk/by-path/ccw-0.0.0201-part1 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD  KEYTABLE=us SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_DASD=0.0.0102 rd_NO_LVM rd_DASD=0.0.0201 rd_NO_DM"