ci(local): curl in the Alpine smoke image

The unified smoke-local.sh readiness-polls the fixture server with
curl; the Alpine image never had it, so every poll iteration failed
command-not-found and the portable smoke leg reported 'fixture server
did not serve' with a perfectly healthy server. Local-only image (CI
portable smokes run on ubuntu runners, curl preinstalled).

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

test-infrastructure/Dockerfile.alpine

@@ -14,6 +14,7 @@ RUN apk add --no-cache \
     zlib-dev \
     zlib-static \
     bash \
+    curl \
     git \
     python3 \
     nodejs \