peer_id not exist

I'm seeing this error message in my logs very frequently:
```
braft/Source/src/braft/node.cpp:1457] node main::650460249 request PreVote from ::650460249 error: [E2][:][E2]peer_id not exist
```

The status page for the source host shows that it is not connected to anything. The status page for one of the destination hosts mentioned in the log shows that it is connected to several other hosts an appears healthy.

I tried looking at the brpc issues on github, but I didn't see anything relevant there. Any hits about this error would be appreciated.

Start at braft/Source/src/braft/node.cpp around line 1457 and compare the source and destination host status pages described in the report. Trace the reported PreVote and peer_id not exist condition; done requires identifying its cause and documenting a concrete next step.

Written by the indexing model from the issue text.