Travis: Fix tests (again)

The problem is that in Go < 1.9 "..." also matches the vendor directory,
and we don't want to run those tests :)

.travis.yml

@@ -29,7 +29,7 @@ install:
 
 script:
   - go install
-  - go test -v ./...
+  - go test -v . ./cmd/rest-server
   - go run build.go -v -T
   - diff <(goimports -d *.go) <(printf "")
 

build.go

@@ -49,7 +49,10 @@ var config = Config{
 	Name:      "rest-server",                                   // name of the program executable and directory
 	Namespace: "github.com/restic/rest-server",                 // subdir of GOPATH, e.g. "github.com/foo/bar"
 	Main:      "github.com/restic/rest-server/cmd/rest-server", // package name for the main package
-	Tests:      []string{"github.com/restic/rest-server/..."},   // tests to run
+	Tests: []string{ // tests to run
+		"github.com/restic/rest-server",
+		"github.com/restic/rest-server/cmd/rest-server",
+	},
 	MinVersion: GoVersion{Major: 1, Minor: 7, Patch: 0}, // minimum Go version supported
 }