Add curl and jq for vttablet-preStop.sh

[rcrowley]

We (definitely) need curl and (ideally) jq, too, in order to do our in-place tablet-rolling via vttablet-preStop.sh. So this patch adds curl and jq to the mysqld_exporter container image.

Here's a live container from before this patch:

█ acre:~/src/planetscale/mysqld_exporter % pskr -n user-data exec
vttablet-aws-uswest2a-5-2398428221-2f828e4c -c mysqld-exporter -- which
which
/usr/bin/which
█ acre:~/src/planetscale/mysqld_exporter % pskr -n user-data exec
vttablet-aws-uswest2a-5-2398428221-2f828e4c -c mysqld-exporter -- which
curl
command terminated with exit code 1
█ acre:~/src/planetscale/mysqld_exporter % pskr -n user-data exec
vttablet-aws-uswest2a-5-2398428221-2f828e4c -c mysqld-exporter -- which
jq
command terminated with exit code 1
█ acre:~/src/planetscale/mysqld_exporter %

And here's a new container with this patch:

█ acre:~/src/planetscale/mysqld_exporter % docker buildx build -t
mysqld_exporter:test .
...
█ acre:~/src/planetscale/mysqld_exporter % docker run --entrypoint which
-i -t mysqld_exporter:test which
/usr/bin/which
█ acre:~/src/planetscale/mysqld_exporter % docker run --entrypoint which
-i -t mysqld_exporter:test curl
/usr/bin/curl
█ acre:~/src/planetscale/mysqld_exporter % docker run --entrypoint which
-i -t mysqld_exporter:test jq
/usr/bin/jq
█ acre:~/src/planetscale/mysqld_exporter %

[maxenglander]

is this required for anything or just a nice to have?

[rcrowley]

Oops. It's a non-functional change I had teed up in my work tree in case I ever needed a dummy change to force the CI through another loop. I actually like it being in because otherwise the working directory is /go which is harmless but kind of nonsense.