Avoid unneeded GetMSTGT() calls in cc_mslsa.c

Both lcc_resolve() and lcc_get_principal() were using GetMSTGT()
to fetch a ticket from which to obtain the client principal name
of the credentials cache.  However, that name is contained in
the results of the the cache information query; there is no need
to retrieve a full ticket of any sort to get it.  Since there
may sometimes be difficulties obtaining a TGT when UAC is enabled,
avoid these unneeded calls.

ticket: 7989