cmd/tendermint: fix initialization file creation checks (#991)

* cmd/tendermint: fix initialization file creation checks

Fixes #989.

The original initialization sequence started to inexplicably
fail
```shell
tendermint unsafe_reset_all
tendermint init
tendermint node --proxy_app=dummy
```

used to fail with
```shell
ERROR: Failed to create node: Couldn't read GenesisDoc file: open
/Users/emmanuelodeke/.tendermint/genesis.json: no such file or directory
```

because the initialization sequence always assumed that the
genesisDoc would only be set if the privValidator was generated.

However, `tendermint unsafe_reset_all` only created the
`priv_validator.json` file which would mean that then running
`tendermint init` would never create the `genesis.json` file
which if following the recommended sequence would then fail
since the `genesis.json` was absent.

* cmd/tendermint: Load PrivValidatorFS if existent, lest generate it

Feedback from @melekes

* change logging messages for init cmd

Refs #989

cmd/tendermint/commands/init.go

@@ -1,8 +1,6 @@
 package commands
 
 import (
-	"os"
-
 	"github.com/spf13/cobra"
 
 	"github.com/tendermint/tendermint/types"
@@ -17,29 +15,34 @@ var InitFilesCmd = &cobra.Command{
 }
 
 func initFiles(cmd *cobra.Command, args []string) {
+	// private validator
 	privValFile := config.PrivValidatorFile()
-	if _, err := os.Stat(privValFile); os.IsNotExist(err) {
-		privValidator := types.GenPrivValidatorFS(privValFile)
+	var privValidator *types.PrivValidatorFS
+	if cmn.FileExists(privValFile) {
+		privValidator = types.LoadPrivValidatorFS(privValFile)
+		logger.Info("Found private validator", "path", privValFile)
+	} else {
+		privValidator = types.GenPrivValidatorFS(privValFile)
 		privValidator.Save()
+		logger.Info("Genetated private validator", "path", privValFile)
+	}
 
-		genFile := config.GenesisFile()
-
-		if _, err := os.Stat(genFile); os.IsNotExist(err) {
-			genDoc := types.GenesisDoc{
-				ChainID: cmn.Fmt("test-chain-%v", cmn.RandStr(6)),
-			}
-			genDoc.Validators = []types.GenesisValidator{{
-				PubKey: privValidator.GetPubKey(),
-				Power:  10,
-			}}
-
-			if err := genDoc.SaveAs(genFile); err != nil {
-				panic(err)
-			}
+	// genesis file
+	genFile := config.GenesisFile()
+	if cmn.FileExists(genFile) {
+		logger.Info("Found genesis file", "path", genFile)
+	} else {
+		genDoc := types.GenesisDoc{
+			ChainID: cmn.Fmt("test-chain-%v", cmn.RandStr(6)),
 		}
+		genDoc.Validators = []types.GenesisValidator{{
+			PubKey: privValidator.GetPubKey(),
+			Power:  10,
+		}}
 
-		logger.Info("Initialized tendermint", "genesis", config.GenesisFile(), "priv_validator", config.PrivValidatorFile())
-	} else {
-		logger.Info("Already initialized", "priv_validator", config.PrivValidatorFile())
+		if err := genDoc.SaveAs(genFile); err != nil {
+			panic(err)
+		}
+		logger.Info("Genetated genesis file", "path", genFile)
 	}
 }