walletimport: doesn't understand erc55 addresses in the dump format

## Summary

- `walletimport` doesn't understand 0x addresses in the dump and as such the import fails.
- `walletdump` after generation of addresses (`getnewaddress`) beyond the original key pool will also generate ERC55.

### To reproduce

- Create a new wallet.
- Generate a few addresses with `getnewaddress`
- `dumpwallet`
- Attempt to reimport it again with `importwallet`

### Temporary workaround

- Using a regex replace to remove the erc55 addresses should make the dump file important again.
- Eg: `sed "s/\(addr=\w\+\),0x\w\+/\1/g" wallet.dump > wallet.importable.dump` to generate a new importable file.