(ITS#6627) Empty suffix and dn for root node should be avoided

[lapsap7+bug@gmail.com]

Full_Name: SEAK T.F.
Version: 2.4.18
OS: Windows XP/7 & Ubuntu 9
URL: 
Submission from: (NULL) (213.41.124.254)


Currently it is possible to create a DIT with empty suffix and empty dn for root
node!  Side-note: Such DIT can be used for redirection.

I've no idea what LDAP standards state, but common sense tells me that name-less
node doesn't make sense.  It's as meaningless as creating a name-less directory
or name-less file.

So, when such incorrect parameters are supplied in the conf file, OpenLDAP
service should not start and should exit with error.