raft: use local LSN in relay recovery restart

When a Raft node is elected as a leader, it should resend all its
data to the followers from the last acked vclock. Because while
the node was not a leader, the other instances ignored all the
changes from it.

The resending is done via restart of the recovery cursor in the
relay thread. When the cursor was restarted, it used the last
acked vclock to find the needed xlog file. But it didn't set the
local LSN component, which was 0 (replicas don't send it).

When in reality the component was not zero, the recovery cursor
still tried to find the oldest xlog file having the first local
row. And it couldn't. The first created local row may be gone long
time ago.

The patch makes the restart keep the local LSN component
unchanged, as it was used by the previous recovery cursor, before
the restart.

Closes #5433