Use alpine:3.9 to fix chromium segfaults

On alpine:3.8 chromium (68.0.3440.75-r0) segfaults even when just using
`chromium-browser --version`. See
https://bugs.alpinelinux.org/issues/9161

alpine:3.9 shipps chromium 72.0.3626.109 which fixes the issue.

test/Dockerfile

-FROM alpine:3.8
+FROM alpine:3.9
 
 LABEL Name="Openappstack bootstrap CI test image"
-LABEL version="0.0.2"
+LABEL version="3.9"
 LABEL vendor1="Greenhost"
 
 RUN apk --no-cache add \