ipa-kdb: protect against context corruption
    
    Early in startup LDAP server might not respond well yet and
    should_support_pac_tkt_sign() will bail out with
    KRB5_KDB_SERVER_INTERNAL_ERR. We should postpone this call but for time
    being we should prevent a crash.
    
    Crash happens because init_module() returns with an error and KDC then
    calls fini_module() which will free the DB context which is already
    corrupted for some reason.
    
    Do not call any free() call because the whole context is corrupted as
    tests do show.
    
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Julien Rische <jrische@redhat.com>