The 389-ds replication plugin may not be installed on all platforms
and our replication version plugin will cause 389-ds to not start
if it is loaded and the replication plugin is not. So disable by
default.

When a replica is prepared we check for the replication plugin.
If it exists we will enable the replication version plugin.

Likewise on installation of a replica we check for existence of
the repliation plugin and if it is there then we enable the version
plugin before replication begins.

ticket 918

Whenever we upgrade IPA such that any data incompatibilities might occur
then we need to bump the DATA_VERSION value so that data will not
replicate to other servers. The idea is that you can do an in-place
upgrade of each IPA server and the different versions own't pollute
each other with bad data.