scripts/test-release.sh should support an argument

[tenmoves]

Is your feature request related to a problem?

Right now we create 2 erlang vms to test the release, we want to extend this functionality and make the script accept an integer argument and create as many erlang vms as this argument.

Describe the solution you'd like

refactor the script to accept a integer as argument and create as many vms.
argument should be between 1 and 8.
scripts/test-release.sh --instances 5 should create 5 vm instances
scripts/test-release.sh --instances 0 should return an error (value not between 1 and 8)

[Neylix]

Issue fixed by #1117