Update WebhookStash sample-function to use new approach

    I used AlpineFunction as the example to follow as suggested by
    @alexellis

Signed-off-by: scott.eppler <scott.eppler@coda.global>

sample-functions/WebhookStash/Dockerfile

+FROM openfaas/classic-watchdog:0.14.4 as watchdog
+
 FROM golang:1.11-alpine as builder
 ENV CGO_ENABLED=0
 
@@ -7,14 +9,13 @@ ENTRYPOINT []
 WORKDIR /go/src/github.com/openfaas/faas/sample-functions/WebhookStash
 
 COPY handler.go .
-# COPY vendor vendor
 
 RUN go install
 
-FROM functions/alpine:latest
+FROM alpine:3.10
 
-# Needed to reach the hub
-RUN apk --no-cache add ca-certificates 
+COPY --from=watchdog /fwatchdog /usr/bin/fwatchdog
+RUN chmod +x /usr/bin/fwatchdog
 
 COPY --from=builder /go/bin/WebhookStash  /usr/bin/WebhookStash
 ENV fprocess "/usr/bin/WebhookStash"