preseed `priv_validator_state.json` when not found

[Andrey Arapov]

There is a known tendermint issue which is not letting some chains to start unless priv_validator_state.json has been manually created.

[node-0] + exec /bin/sh -c '$START_CMD'
[node-0] 8:39PM INF running app args=["start"] module=cosmovisor path=/root/.sifnoded/cosmovisor/genesis/bin/sifnoded
[node-0] 8:39PM INF starting node with ABCI Tendermint in-process
[node-0] open /root/.sifnoded/data/priv_validator_state.json: no such file or directory
[node-0] Error: exit status 1
[node-0] 8:39PM ERR error="exit status 1" module=cosmovisor

Workaround:

mkdir /root/.sifnoded/data
echo '{"height":"0","round":0,"step":0}' > /root/.sifnoded/data/priv_validator_state.json