[Scripts] Ensure docker is running before starting localstack

Summary:
Localstack failing to start because docker isn't available
is not a good user experience as it outputs a bunch of "cannot open
socket" errors.

As part of starting localstack, ensure that docker is available before
attempting to launch localstack

https://linear.app/comm/issue/ENG-3227

Test Plan:

# Stop docker
comm-dev services start
# Get message about starting docker

# Start docker
comm-dev services start
# Localstack starts

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7384