Trim v from OS version. (#231)

* Trim v from OS version.

* Add go strings pkg.

* Revert logging.

trusted_os/main.go

@@ -23,6 +23,7 @@ import (
 	"log"
 	"os"
 	"runtime"
+	"strings"
 	"time"
 
 	"github.com/coreos/go-semver/semver"
@@ -194,7 +195,7 @@ func main() {
 		log.Fatalf("SM failed to create OS bundle verifier: %v", err)
 	}
 
-	if v, err := semver.NewVersion(Version); err != nil {
+	if v, err := semver.NewVersion(strings.TrimPrefix(Version, "v")); err != nil {
 		log.Printf("Failed to parse OS version %q: %v", Version, err)
 	} else {
 		osVersion = *v