BDRVReplicationState.replication_state is a name with a bit of
duplication, plus it could be an enum like BDRVReplicationState.mode,
which is more readable and also more straightforward in a debugger.
Rename it, and improve the type while at it.
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>