fix '|&' shell pipe on travis osx vm

'|&' is despite syntax error on travis osx vm, but test passes.
Fix avoid sdboyer/gps testdata error message using 2>&1

Signed-off-by: Koichi Shiraishi <[email protected]>

Author: zchee

.travis.yml

@@ -16,7 +16,7 @@
   script:
     - go build -v
     - go vet $(go list ./... | grep -v vendor)
-    - test -z "$(gofmt -s -l . |& grep -v vendor | tee /dev/stderr)"
+    - test -z "$(gofmt -s -l . 2>&1 | grep -v vendor | tee /dev/stderr)"
     - go test $(go list ./... | grep -v vendor)
     - go build ./hack/licenseok
     - find . -path ./vendor -prune -o -type f -name "*.go" -printf '%P\n' | xargs ./licenseok