IPA-KDB: use relative path in ipa-certmap config snippet
    
    Architecture specific paths should be avoided in the global Kerberos
    configuration because it is read e.g. by 32bit and 64bit libraries they
    are installed in parallel.
    
    Resolves https://pagure.io/freeipa/issue/6833
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>