deploy script's check for redis is unreliable

[xhluca]

Right now, this is how we check if redis is used:

dash-sample-apps/deploy

Lines 107 to 108 in c9c676a

	[[ -n "$celery_version" ]] && log-info "celery python version: $(cat "$app_dir/requirements.txt" | grep -E "^celery=")"
	[[ -n "$redis_version" ]] && log-info "redis python version: $(cat "$app_dir/requirements.txt" | grep -E "^redis=")"

This is not reliable since I might not include redis inside requirements.txt - in some of the recent apps I had to move all the requirements to another file and install them on the fly with a predeploy.sh script; in this scenario it would've been missed.