Implement cccol iterators for mslsa

Also implement  switch_to stub

Signed-off-by: Kevin Wasserman <kevin.wasserman@painless-security.com>

https://github.com/krb5/krb5/commit/218193bb93d8cf9fd82087533c45602b6a8c5151
Author: Kevin Wasserman <kevin.wasserman@painless-security.com>
Committer: Sam Hartman <hartmans@mit.edu>
Commit: 218193bb93d8cf9fd82087533c45602b6a8c5151
Branch: master
 src/lib/krb5/ccache/cc_mslsa.c |   68 +++++++++++++++++++++++++++++++++++----
 1 files changed, 61 insertions(+), 7 deletions(-)