Reorder XML-RPC initialization in ipa-join to avoid segfault.
    
    There were a number of code paths where we would try to call
    xmlrpc_env_clean() without having first called xmlrpc_env_init()
    Re-order the code so we always initialize the XML-RPC client first.
    
    I also noticed a place where the return value of strdup() was not
    being checked for NULL.
    
    https://fedorahosted.org/freeipa/ticket/3275