Previously chef-client died if /etc/krb5.keytab is not present, to prevent
pam-config from getting deployed if it cannot work. This also inhibited
installation of wallet-client and /etc/krb5.conf

This switch is now in recipes/pam.rb, where pam-update-config with the name
'Kerberos authentication' is not added when /etc/krb5.keytab is not
available. However /etc/krb5.conf is written and wallet-client is installed.