Bug 767273 - add switch to disable DN normalization of nested DNs
    
    https://bugzilla.redhat.com/show_bug.cgi?id=767273
    Resolves: bug 767273
    Bug Description: add switch to disable DN normalization of nested DNs
    Reviewed by: nhosoi (Thanks!)
    Branch: Directory_Server_8_2_Branch
    Fix Description: Added a new cn=config attribute nsslapd-normalize-nested-dn
    This is set to "on" by default.  If this is set to off, the old (8.2.2)
    version of slapi_normalize_dn_ext() will be used instead of the new one.
    Platforms tested: RHEL6 x86_64
    Flag Day: no
    Doc impact: no
    cherry-picked from 45623ad410327af106eaf5a50a1149d3c01fc54d and rebased for 8.2