Fix for  issue #2829 (Problems configuring and unconfiguring replication servers)
scenario:
 1) configure and start 2 servers s1 and s2
 2) enable the replication between them
 3) disable replication on server s1
 4) disable replication on server s2
 5) re-enable the replication between them

we've got an error on step 5

The root cause is actually on step 3, when the replication is disabled
on server s1: all references to s1, including the s1 public instance
key, are removed from "cn=admin data" on all servers. To do that, we
just remove the info on one server, and the replication protocol will
propagate it on all the other.
The drawback (actually the issue) is that this public instance key is
indirectly used by several components. At least, the replication
protocol itself required the key to establish the connection between
replication servers on s1 and s2.
So, when we try to re-enable the replication the s1 public instance
key cannot be found and we've got the error.


fix:
At the end of the disable-replication process, we add again the
previously removed public instance key.