Ticket #48822 - (389-ds-base-1.3.5) Fixing coverity issues.
    
    Description: Invalid Dereference
    - FORWARD_NULL: slapd/schema.c:4758:5: deref_parm: Directly dereferencing
      parameter "oc".
      ==> Fixed so that null oc never be passed to parse_objclass_str.
    - FORWARD_NULL: slapd/pw.c:2880: var_deref_op: Dereferencing null pointer "e".
      ==> Fixed the logic error.
    - REVERSE_INULL: slapd/extendop.c:384: check_after_deref: Null-checking
      "be_pb" suggests that it may be null, but it has already been dereferenced
      on all paths leading to the check.
      ==> Removed the unnecessary NULL check.
    - FORWARD_NULL: slapd/entry.c:2118:2: deref_parm: Directly dereferencing
      parameter "e".
      ==> Fixed so that null e never be passed to referint_validate_config.
    - FORWARD_NULL: slapd/back-ldbm/ldif2ldbm.c:1166: var_deref_op: Dereferencing
      null pointer "be".
      ==> Added a null check for be.
    - REVERSE_INULL: plugins/acl/aclutil.c:221: check_after_deref: Null-checking
      "dn" suggests that it may be null, but it has already been dereferenced on
      all paths leading to the check.
      ==> Moved the null dn check prior to all the dn access.
    
    https://fedorahosted.org/389/ticket/48822
    
    Reviewed by wibrown@redhat.com (Thank you, William!!)