[krbdev.mit.edu #7810] Tests broken on CentOS 6 in 1.12

[Andrea Campi via RT]

Hi,

this commit:

https://github.com/krb5/krb5/commit/5d03cb6b235f0ee0e30b34630f95f208d6acd3d0
commit 5d03cb6b235f0ee0e30b34630f95f208d6acd3d0
Author: Greg Hudson <ghudson at mit.edu>
Date:   Sat Sep 28 16:29:36 2013 -0400

    Conditionally test KEYRING ccache type



started using "keyctl purge".
But the purge subcommand seems not to be available on e.g. CentOS 6
(keyutils-1.4-4.el6.x86_64).

Andrea