core: Engine is sending bad credentials repeatdely

In some errors (like wrong credentials) engine should
not try to work with the next ldap server, unfortunately
this information (that it should not try the next ldap server)
is only logged , and it continues to the next ldap server
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1085529
Change-Id: I9c04d586a776b469f0e619d3ea0ff844ea07a357
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>