Increase default file handle limits for daemons
    
    Linux still defaults to a 1024 open file handle limit. This causes
    scalability problems for libvirtd / virtlockd / virtlogd on large
    hosts which might want > 1024 guest to be running. In fact if each
    guest needs > 1 FD, we can't even get to 500 guests. This is not
    good enough when we see machines with 100's of physical cores and
    TBs of RAM.
    
    In comparison to other memory requirements of libvirtd & related
    daemons, the resource usage associated with open file handles
    is essentially line noise. It is thus reasonable to increase the
    limits unconditionally for all installs.
    
    Signed-off-by: Daniel P. Berrange <berrange@redhat.com>