kernel-install: do not require non-empty kernel cmdline
    
    When booting with Fedora-Server-dvd-x86_64-30-20190411.n.0.iso,
    /proc/cmdline is empty (libvirt, qemu host with bios, not sure if that
    matters), after installation to disk, anaconda would "crash" in kernel-core
    %posttrans, after calling kernel-install, because dracut would fail
    with
    
    > Could not determine the kernel command line parameters.
    > Please specify the kernel command line in /etc/kernel/cmdline!
    
    I guess it's legitimate, even if unusual, to have no cmdline parameters.
    Two changes are done in this patch:
    
    1. do not fail if the cmdline is empty.
    2. if /usr/lib/kernel/cmdline or /etc/kernel/cmdline are present, but
       empty, ignore /proc/cmdline. If there's explicit configuration to
       have empty cmdline, don't ignore it.
    
    The same change was done in dracut:
    https://github.com/dracutdevs/dracut/pull/561.
    
    (cherry picked from commit 88e1306af6380794842fb31108ba67895799fab4)
    
    Resolves: #1701454
    
    patch_name: 0224-kernel-install-do-not-require-non-empty-kernel-cmdli.patch
    present_in_specfile: true
    location_in_specfile: 224
    squash_commits: true