[reconfig] Do not respawn node sync process

[lxfind]

Node sync process only runs on fullnode, while reconfiguration only happens on a validator.

[mystenmark]

reconfiguration only happens on a validator

Ok, this was my bad - I thought that nodes would follow the same reconfig process as validators when the epoch changes. If they won't, we certainly don't need this. But we will need an analogous function that fullnodes run when they switch to a new epoch.

Also, there is a piece that we do need to re-start after reconfig, which is the creation of NodeSyncState (here: https://github.com/MystenLabs/sui/blob/main/crates/sui-core/src/authority_active.rs#L286) - that piece does run on validators and will have to be re-created or otherwise reconfigured, since it holds an AuthorityAggregator and Committee.

But that's for another PR.