make kompose exit with 1 if error (#1343)

Old code passes -1 to os.Exit and the value is directly passed to syscall.
The behavior with -1 depends on environments (most cases should convert
into 255 though)

This commit is to remove unnecessary the ambiguity and change it to use 1 instead of 255.

main.go

@@ -16,8 +16,15 @@ limitations under the License.
 
 package main
 
-import "github.com/kubernetes/kompose/cmd"
+import (
+	"log"
+
+	"github.com/kubernetes/kompose/cmd"
+)
 
 func main() {
-	cmd.Execute()
+	if err := cmd.Execute(); err != nil {
+		log.SetFlags(0)
+		log.Fatal(err)
+	}
 }