auth: Add the ktc_ListTokensEx function

auth: Add the ktc_ListTokensEx function

Add a ktc_ListTokensEx function which uses the new GetToken pioctl
to implement the same functionality as the old ktc_ListTokens call.

As with ktc_ListTokens this is hugely inefficient, as it gets a
compelete token structure from the kernel, then throws it away to
return just the cell which the token is for.

Change-Id: Idf3daa536c6a04d397691d0cc6fcb2c59f9f444c
Reviewed-on: http://gerrit.openafs.org/2748
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>