Ticket 49105 - Sig FPE when ns-slapd has 0 backends.
Bug Description: The autotuning system assumed we had 1 or more backends.
As a result, when you start a server with no backends, a divide by 0 was
encountered
Fix Description: Check the backend count before we attempt the division.
https://fedorahosted.org/389/ticket/49105
Author: wibrown
Review by: nhosoi (Thanks!)