Issue with setup_agent.sh file

[MajorasJack]

**Output of the info page **

N/A

Additional environment details (Operating System, Cloud provider, etc):
N/A

Steps to reproduce the issue:

1. Attempt to run the https://github.com/DataDog/dd-agent/blob/master/packaging/datadog-agent/source/setup_agent.sh script on any setup
2. Can also just run this dockerfile: https://hub.docker.com/r/datadog/docker-dd-agent/dockerfile/

Describe the results you received:

Describe the results you expected:
Successful installation

Additional information you deem important (e.g. issue happens only occasionally):
dl.bintray.com & bintray have been deprecated and taken offline, so an alternative hosting is required for the jmxfetch jarfile (preferably stored at Datadog instead of a third party to prevent this happening again)