Use conditional build for retrieving ccache.
    
    Some krb5 functions needn't be available for retrieving ccache
    with principal. Therefore ifdef is used to solve this situation with older
    version of libkrb5. There were two functions with similar functionality
    in krb5_child and krb5_utils. They were merged to one universal function, which
    was moved to file src/util/sss_krb5.c