Minor cn=config nsslapd-haproxy-trusted-ip issues

[droideck]

Issue Description
This ticket is for fixing minor issues with the nsslapd-haproxy-trusted-ip attribute.
Issues:

• It is not present in cn=config by default.
• It is not present in cn=schema.
• Deleting a single value from the attribute doesn't work and requires server restart to get rid of the attribute.

We need to investigate the issues and decide how the behaviour should be defined (as our cn=config processing is different from usual LDAP modify operations)

[droideck]

Okay, for It is not present in cn=schema. - the PR is ready.

For the rest of the reported issues:

It is not present in cn=config by default.

We don't display the attribute if it doesn't have a value. So ldapsearch -xLLL -D "cn=Directory Manager" -w password -H ldap://localhost:389 -b cn=config nsslapd-haproxy-trusted-ip | grep haproxy will naturally fail as expected (nothing is found).
But when the value is set, the ldapsearch will find the line.

Deleting a single value from the attribute doesn't work and requires server restart to get rid of the attribute.

Looks like it actually happens because of the old issue - #2078
I think this issue should be fixed as part of the #2078 ticket to avoid duplicates and cover all cases.
It is a low priority, though.

[droideck]

b6c2d78..245ffc0 389-ds-base-3.0 -> 389-ds-base-3.0
fad9ff3..6c7047a 389-ds-base-2.5 -> 389-ds-base-2.5
0e19d4e..2884c27 389-ds-base-2.4 -> 389-ds-base-2.4
3c78133..0160710 389-ds-base-1.4.3 -> 389-ds-base-1.4.3