Problem:
    mysqld --collation-server=xxx --character-set-server=yyy
    didn't work as expected: collation_server was set not to xxx,
    but to the default collation of character set "yyy".
    
    With different argument order it worked as expected:
    mysqld --character-set-server=yyy --collation-server=yyy 
    
    Fix:
    initializate default_collation_name to 0
    when processing --character-set-server
    only if --collation-server has not been specified
    in command line.