introduce the auto_reset_crashkernel option to kdump.conf
    
    This option will determine whether to reset kernel crashkernel
    to new default value or not when kexec-tools updates the default
    crashkernel value and existing kernels using the old default kernel
    crashkernel value. Default to yes.
    
    Reviewed-by: Pingfan Liu <piliu@redhat.com>
    Reviewed-by: Philipp Rudo <prudo@redhat.com>
    Signed-off-by: Coiby Xu <coxu@redhat.com>