krb5-wrap: Use the principal returned by the KDC to create the ccache

krb5-wrap: Use the principal returned by the KDC to create the ccache

We request a TGT in uppercase from the KDC. We turned on
canonicalization for that so the KDC returns the principal in lowercase
cause of this. As we use the uppercase prinicpal to create the ccache we
fail to find the tickets we need later because it is stored in the
incorrect case. You have to use the princial returned by the KDC here.

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>