[alias-server] Unit tests for main.js

Summary:
T3060

Depends on D13644

Add unit tests for main

Patch bug found by introduction of test to correctly pass address param

Test Plan:
npm test
node index.js`, app starts up, waits 10s, gives block height and hash of avalanche final block

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13645