migration/docs: Update postcopy recover session for SETUP phase

migration/docs: Update postcopy recover session for SETUP phase

Firstly, the "Paused" state was added in the wrong place before. The state
machine section was describing PostcopyState, rather than MigrationStatus.
Drop the Paused state descriptions.

Then in the postcopy recover session, add more information on the state
machine for MigrationStatus in the lines.  Add the new RECOVER_SETUP phase.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
[fix typo s/reconnects/reconnect]
Signed-off-by: Fabiano Rosas <farosas@suse.de>