test: add more repos to clone test

- parallelize test tasks to number of cores
- `git pull` instead of `git clone` on later test runs

git:// tries to use ssh behind the scenes which is usually blocked by corporate networks.  https:// tends not to be so use that instead.

This prevents this sort of error:

```
npm ERR! git fetch -a origin (git://github.com/eslint/eslint.git) fatal: unable to connect to github.com:
npm ERR! git fetch -a origin (git://github.com/eslint/eslint.git) github.com[0: 192.30.252.131]: errno=Operation timed out
npm ERR! Error: Command failed: fatal: unable to connect to github.com:
npm ERR! github.com[0: 192.30.252.131]: errno=Operation timed out
```

Use https:// link for eslint tarball instead of git://