Fix conversions of bit lengths to byte lengths
    
    Fix a number of places where we weren't correctly converting from length
    in bits to length in bytes, and one in the self-tests where the newest
    version of NSS complains if the size of a signature was too large
    because it was not converted at all.
    
    Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>