Properly handle LDAP socket closures in ipa-otpd
In at least one case, when an LDAP socket closes, a read event is fired
rather than an error event. Without this patch, ipa-otpd silently
ignores this event and enters a state where all bind auths fail.
To remedy this problem, we pass error events along the same path as read
events. Should the actual read fail, we exit.
https://bugzilla.redhat.com/show_bug.cgi?id=1377858
https://fedorahosted.org/freeipa/ticket/6368
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>