Do not store build host name in initrd
    
    Without this patch, kernel-obs-build stored the build host name
    in its .build.initrd.kvm
    
    This patch allows for reproducible builds of kernel-obs-build and thus
    avoids re-publishing the kernel-obs-build.rpm when nothing changed.
    
    Note that this has no influence on the /etc/hosts file
    that is used during other OBS builds.
    
    https://bugzilla.opensuse.org/show_bug.cgi?id=1084909
    
    Signed-off-by: Bernhard M. Wiedemann <bwiedemann@suse.de>