fix broken test.sh node image replacement logic

[donstephan]

This fixes tests for PR #161. The test.sh file did not handle swapping in the node image maintained by meteor for version 14.21.4.

[donstephan]

Output includes which registry it's using:

Output from 2.16: https://github.com/disney/meteor-base/actions/runs/10078450028/job/27863413913?pr=162

Testing Docker image geoffreybooth/meteor-base:2.16...
Creating test app...
Using Meteor fork of Node Docker image...
Building test app Docker image...
Launching test app...
Running test...
PASS for geoffreybooth/meteor-base:2.16 with meteor/node:14.21.4-alpine3.17 after 1 min 53 sec
PASS! All images passed the test

Output from 2.9.1: https://github.com/disney/meteor-base/actions/runs/10078450028/job/27863409388?pr=162

Testing Docker image geoffreybooth/meteor-base:2.9.1...
Creating test app...
Using official Node Docker image...
Building test app Docker image...
Launching test app...
Running test...
PASS for geoffreybooth/meteor-base:2.[9](https://github.com/disney/meteor-base/actions/runs/10078450028/job/27863409388?pr=162#step:4:10).1 with node:14.21.2-alpine after 1 min 36 sec
PASS! All images passed the test