Ticket #47367 - (phase 1) ldapdelete returns non-leaf entry error while trying to remove a leaf entry
    
    Bug description: Replication conflict confuses the numsubordinate count,
    which leaves an entry that cannot be deleted even its subordinate entries
    are all removed.
    
    Fix description:
    [urp.c] 1) get_dn_plus_uniqueid: a logic to create a conflict DN had a bug.
      It used to call slapi_sdn_get_rdn to get the rdn.  The function slapi_sdn_
      get_rdn blindly returned the "dn" field without checking whether the field
      is NULL or not.  Instead, this patch changes the interface of the helper
      function get_dn_plus_uniqueid and use the original Slapi_DN with slapi_sdn_
      get_dn, then generates the conflict DN "nsuniqueid=...+ <RDN>,<PARENT>".
      2) The urp calling timing was moved from SLAPI_PLUGIN_BE_TXN_PRE_* to
      SLAPI_PLUGIN_BE_PRE_*.  (Note: SLAPI_PLUGIN_BE_PRE_* is also in the
      backend transaction.)  This is necessary since urp needs to be done
      prior to parent checking.
    [ldbm_add.c] Moved SLAPI_PLUGIN_BE_PRE_ADD_FN inside of the transaction.
      Other operations are already calling SLAPI_PLUGIN_BE_PRE function at the
      timing.
    [ldbm_delete.c] There is a case a parent of a delete-candidate entry runs
      into a conflict and multiple parent entries exist.  Once it occurs, a
      parent entry found by the parent dn string may not be the entry which
      manages the numsubordinate count the delete-candidate entry belonging to.
      It confuses the numsubordinate counts and leaves an entry which cannot be
      deleted due to the numsubordinate count mismatch. This patch retrieves
      parent entry by parent id if it is available.
    [ldbm_entryrdn.c] When traversing the DIT, a special treatment is needed
      for a tombstone entry. I.e, 2 RDNs (nsuniqueid=..., <RDN>) is treated as
      one RDN.  It should decrement the index (rdnidx) one more to point to the
      right position of the RDN array in Slapi_RDN.
    [ldbm_search.c] When checking the scope of an entry in ldbm_back_next_
      search_entry_ext, a tombstone entry was not properly examined. This patch
      introduces a new slapi api slapi_sdn_scope_test_ext.
    [dn.c] In slapi_sdn_get_rdn, use slapi_sdn_get_dn to get the dn value of
      Slapi_DN.  It was one cause of the problem in get_dn_plus_uniqueid (urp.c).
      This patch adds slapi_sdn_scope_test_ext, which takes flags to indicates
      the first argument dn is a tombstone sdn.  Also, this patch replaces
      "malloc + strcpy + strcat" with slapi_ch_smprintf to improve the
      readability of the code.
    [rdn.c] This patch replaces "malloc + strcpy + strcat" with slapi_create_
      dn_string to normalize the newly added rdn and improve the readability of
      the code.
    
    Reviewed by Rich (Thanks!!)
    
    https://fedorahosted.org/389/ticket/47367
    (cherry picked from commit 2f4f74b3d38eeb38f0794dfb2e880a95e7e9bd49)
    (cherry picked from commit 690d58ba5870e7f0dd3ad6593c92a86771fc54d5)