Modififed NSSConnection not to shutdown existing database.
    
    The NSSConnection class has been modified not to shutdown the
    existing NSS database if the database is already opened to
    establish an SSL connection, or is already opened by another
    code that uses an NSS database without establishing an SSL
    connection such as vault CLIs.
    
    https://fedorahosted.org/freeipa/ticket/4638
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>