At the completion of the while loop the value of 'ret' cannot
be zero. The expected value is KRB5_CC_END. Any other value
is an error to return to the caller. If 'ret' is KRB5_CC_END
then return krcc_end_get() result().
Change-Id: Ic2afb5a754e03d521c10a259c53fc70b86b4a132