replication: enter orphan mode on manual replication configuration chage

Currently we only enter orphan mode when instance fails to connect to
replication_connect_quorum remote instances during local recovery.
On bootstrap and manual replication configuration change an error is
thrown. We better enter orphan mode on manual config change, and leave
it only in case we managed to sync with replication_connect_quorum
instances.

Closes #4424

@TarantoolBot document
Title: document reaction on error in replication configuration change.

Now when issuing `box.cfg{replication={uri1, uri2, ...}}` and failing to
sync with replication_connect_quorum remote instances, the server will
throw an error, if it is bootstrapping, and just set its state to orphan
in all other cases (recovering from existing xlog/snap files or manually
changing box.cfg.replication on the fly). To leave orphan mode, you may
wait until the server manages to sync with replication_connect_quorum
instances.
In order to leave orphan mode you need to make the server sync with
enough instances. To do so, you may either:
1) set replication_connect_quorum to a lower value
2) reset box.cfg.replication to exclude instances that cannot
   be reached or synced with
3) just set box.cfg.replication to "" (empty string)