Fix camget/cammount so they accept --help

Fixes #671

Change-Id: I515f592660772f25993008071c36ed46f8a54920

cmd/camget/camget.go

@@ -58,6 +58,10 @@ func main() {
 	client.AddFlags()
 	flag.Parse()
 
+	if *cmdmain.FlagHelp {
+		flag.PrintDefaults()
+	}
+
 	if *flagVersion {
 		fmt.Fprintf(os.Stderr, "camget version: %s\n", buildinfo.Version())
 		return

cmd/cammount/cammount.go

@@ -70,6 +70,10 @@ func main() {
 		return
 	}
 
+	if *cmdmain.FlagHelp {
+		usage()
+	}
+
 	narg := flag.NArg()
 	if narg > 2 {
 		usage()