Rewrite has_creds
    
    Original has_creds calls krb5_cccol_have_content that is only available since
    version 1.11 of krb5 library, but in EL6, e.g. the CentOS and RHEL6, just an
    old version in the repository. Rewriting has_creds aims to make cccolutils be
    usable in all Fedora dist and both EL6 and EL7.
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>