FIX: test get default ccache method

This fix according to the change to credential cache since Kerberos 1.10

In Kerberos 1.10, credential cache collection was introduced. The default
credential cache is initilaized in directory /run/user/$UID/krb5cc/

More information about this, refer to
http://web.mit.edu/kerberos/krb5-devel/doc/basic/ccache_def.html#collections-of-caches
REV: refine code
REV: bump version 0.3.3-1