cli: grafana-cli should receive flags from the command line (#17606)

grafana-cli should allow configuration overrides to be received from the command line. e.g.

```
grafana-cli admin reset-password cfg:default.paths.logs=custom/log/directory/
```

Seems like we missed the inclusion of `flag.Parse` as we run the command,  to be able to consume them.

Additionally, it'll be useful for the user to know whenever these are being overriden or not - hence the addition of logging the configuration to be used as we run the command.

pkg/cmd/grafana-cli/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"os"
 	"runtime"
@@ -17,6 +18,7 @@ var version = "master"
 func main() {
 	setupLogging()
 
+	flag.Parse()
 	app := cli.NewApp()
 	app.Name = "Grafana cli"
 	app.Usage = ""