Description of problem:
Deleting an indexed multi value attribute and re-adding it with the same value
in the same ldapmodify operation does not update the 'pres' index properly.

Version-Release number of selected component (if applicable):
389-ds-base-1.2.11.15-65.el6_7.x86_64


How reproducible:
Always


Steps to Reproduce:
1. Setup a RHDS server (stand-alone)
2. Create a user:
   # ldapadd -x -h localhost -D 'cn=Directory Manager' -w <password> <<-EOF
   dn: uid=user0099,ou=People,dc=example,dc=com
   givenName: Test
   sn: User
   loginShell: /bin/bash
   uidNumber: 10099
   gidNumber: 10099
   objectClass: top
   objectClass: person
   objectClass: organizationalPerson
   objectClass: inetorgperson
   objectClass: posixAccount
   uid: user0099
   gecos: Test User
   mail: user0099
   mail: alias
   cn: Test User
   homeDirectory: /home/user0099
   EOF

3. Update the mail attribute by deleting all values and add only one value,
   that was previously used, in the same ldapmodify command:
   # ldapmodify -x -h localhost -D 'cn=Directory Manager' -w <password> <<-EOF
   dn: uid=user0099,ou=People,dc=local,dc=redhat,dc=com
   changetype: modify
   delete: mail
   mail: user0099
   mail: alias
   -
   add: mail
   mail: user0099
   EOF
   ;;

4. Search for entries that have 'mail=alias' (i.e. the value that was
   deleted):
   # ldapsearch -LLL -x -h localhost -D 'cn=Directory Manager' -w <password> -b
"dc=example,dc=com" mail=alias cn

5. Check the entry as returned by 4:
   # ldapsearch -LLL -x -h localhost -D 'cn=Directory Manager' -w <password> -b
"dc=example,dc=com" uid=user009 mail



Actual results:
The search in 4. returns the user009 object while the mail attribute for
'alias' has been deleted:
# ldapsearch -LLL -x -h localhost -D 'cn=Directory Manager' -w <password> -b
"dc=example,dc=com" mail=alias cn
dn: uid=user0099,ou=People,dc=local,dc=redhat,dc=com
cn: Test User

The search in 5. shows this object does not contain the deleted mail
attribute:
# ldapsearch -LLL -x -h localhost -D 'cn=Directory Manager' -w <password> -b
"dc=example,dc=com" uid=user009 mail
dn: uid=user0099,ou=People,dc=local,dc=redhat,dc=com
mail: user0099



Expected results:
The search in 4. not to return the user009 object.


Additional info:
A dbscan of the mail index db shows both values (even after the db cache is
flushed):
# dbscan -f /var/lib/dirsrv/slapd-<instance>/db/userRoot/mail.db4 | grep ^=
=alias
=user0099

The 'sub' index as part of the mail index does seems to be updated properly.