fix usage of sed with -i option

* when using sed with -i it's crucial to not put any spaces between -i and SUFFIX
  * good: sed -i.bk ...
  * bad:  sed -i .bk ...
* otherwise this error is shown when using GNU sed 4.2.2:
  sed: -e expression #1, char 1: unknown command: `.'

Makefile

@@ -60,7 +60,7 @@ darwin_dist: packetbeat
 	cp packetbeat packetbeat-$(VERSION)-darwin
 	cp etc/packetbeat.yml packetbeat-$(VERSION)-darwin/
 	cp etc/packetbeat.template.json packetbeat-$(VERSION)-darwin/
-	sed -i .bk 's/device: any/device: en0/' packetbeat-$(VERSION)-darwin/packetbeat.yml
+	sed -i.bk 's/device: any/device: en0/' packetbeat-$(VERSION)-darwin/packetbeat.yml
 	rm packetbeat-$(VERSION)-darwin/packetbeat.yml.bk
 	tar czvf packetbeat-$(VERSION)-darwin.tgz packetbeat-$(VERSION)-darwin
 	shasum packetbeat-$(VERSION)-darwin.tgz > packetbeat-$(VERSION)-darwin.tgz.sha1.txt
@@ -76,7 +76,6 @@ install_cfg:
 	cp etc/packetbeat.yml $(PREFIX)/packetbeat-win.yml
 	sed -i.bk 's/device: any/device: 0/' $(PREFIX)/packetbeat-win.yml
 
-
 .PHONY: gofmt
 gofmt:
 	go fmt ./...
@@ -104,7 +103,6 @@ coverage:
 	GOPATH=$(shell $(GODEP) path):$(GOPATH) $(GOPATH)/bin/gotestcover -coverprofile=./coverage/unit.cov -covermode=count github.com/elastic/packetbeat/...
 	$(GODEP) go tool cover -html=./coverage/unit.cov -o coverage/unit.html
 
-
 .PHONY: benchmark
 benchmark:
 	$(GODEP) go test -short -bench=. ./...

scripts/generate_gettingstarted.sh

@@ -36,8 +36,8 @@ EOF
 
 cat $INPUT >> $OUTPUT
 
-sed -i .bk "s/\$PB_VERSION/$PB_VERSION/g" $OUTPUT
-sed -i .bk "s/\$ES_VERSION/$ES_VERSION/g" $OUTPUT
-sed -i .bk "s/\$KIBANA_VERSION/$KIBANA_VERSION/g" $OUTPUT
-sed -i .bk "s/\$DASHBOARDS_VERSION/$DASHBOARDS_VERSION/g" $OUTPUT
+sed -i.bk "s/\$PB_VERSION/$PB_VERSION/g" $OUTPUT
+sed -i.bk "s/\$ES_VERSION/$ES_VERSION/g" $OUTPUT
+sed -i.bk "s/\$KIBANA_VERSION/$KIBANA_VERSION/g" $OUTPUT
+sed -i.bk "s/\$DASHBOARDS_VERSION/$DASHBOARDS_VERSION/g" $OUTPUT
 rm $OUTPUT.bk