app/vmalert: do not pring description for all the flags on config errors

The description is too big to consume by human and it just distracts humans.

app/vmalert/datasource/init.go

@@ -31,7 +31,6 @@ var (
 // Init creates a Querier from provided flag values.
 func Init() (Querier, error) {
 	if *addr == "" {
-		flag.PrintDefaults()
 		return nil, fmt.Errorf("datasource.url is empty")
 	}
 	tr, err := utils.Transport(*addr, *tlsCertFile, *tlsKeyFile, *tlsCAFile, *tlsServerName, *tlsInsecureSkipVerify)

app/vmalert/notifier/init.go

@@ -26,7 +26,6 @@ var (
 // Init creates a Notifier object based on provided flags.
 func Init(gen AlertURLGenerator) ([]Notifier, error) {
 	if len(*addrs) == 0 {
-		flag.PrintDefaults()
 		return nil, fmt.Errorf("at least one `-notifier.url` must be set")
 	}