Use jq to make parsing GECKODRIVER API call reproducible

[GregSutcliffe]

Description
The curl call to the GitHub API to get the latest release of GECKODRIVER fails intermittently. The call looks like this:

curl -s https://api.github.com/repos/mozilla/geckodriver/releases/latest

On investigation, this appears to be because GitHub itself isn't consistent it how it returns the API data - sometimes it's a nicely formatted output, eg:

# cat good_response.json
{
  "url": "https://api.github.com/repos/mozilla/geckodriver/releases/168891133",
  "assets_url": "https://api.github.com/repos/mozilla/geckodriver/releases/168891133/assets",
  "upload_url": "https://uploads.github.com/repos/mozilla/geckodriver/releases/168891133/assets{?name,label}",
  "html_url": "https://github.com/mozilla/geckodriver/releases/tag/v0.35.0",
...

but sometimes it removes the newlines:

cat bad_response.json
{"url":"https://api.github.com/repos/mozilla/geckodriver/releases/168891133","assets_url":"https://api.github.com/repos/mozilla/geckodriver/releases/168891133/assets","upload_url":"https://uploads.github.com/repos/mozilla/geckodriver/releases/168891133/assets{?name,label}","html_url":"https://github.com/mozilla/geckodriver/releases/tag/v0.35.0"...

This second form causes the grep/sed combo to fail, since the grep now matches the entire output instead of one line.

This PR fixes the issue by using JQ to parse the output, which works regardless of form:

# cat /tmp/good_response.json | jq -r '.tag_name' | sed 's/v//'
0.35.0

# cat /tmp/bad_response.json | jq -r '.tag_name' | sed 's/v//'                                                                                                                         
0.35.0

Signed commits

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[sgoggins]

Awesome!!