selinux-testsuite: do not check kernel RPM
    
    The RPM is not important, what is important is the running kernel (and
    that can't be missing, obviously) and its version is already shown
    elsewhere.
    
    Moe importantly, in Fedora CI the 'kernel' RPM may not even be there, so
    the test would warn about it, causing failures.
    
    Reported-by: Lukas Vrabec <lvrabec@redhat.com>
    Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>