build: fix docker tag to include `v` prefix in version string

build/ci.go

@@ -492,7 +492,7 @@ func doDocker(cmdline []string) {
 	case env.Branch == "master":
 		tags = []string{"latest"}
 	case strings.HasPrefix(env.Tag, "v1."):
-		tags = []string{"stable", fmt.Sprintf("release-1.%d", params.VersionMinor), params.Version}
+		tags = []string{"stable", fmt.Sprintf("release-1.%d", params.VersionMinor), "v" + params.Version}
 	}
 	// If architecture specific image builds are requested, build and push them
 	if *image {