Bump alpine to 3.11

There's a new release which appears to have no apparent down-
sides or breakages.

https://www.alpinelinux.org/posts/Alpine-3.11.2-released.html

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

sample-functions/WordCountFunction/Dockerfile

@@ -1,5 +1,10 @@
 FROM functions/alpine:latest
 
+USER root
+
 # Populate example here
 ENV fprocess="wc"
+
+USER 1000
+
 CMD ["fwatchdog"]