Add support for self-signed certificates

[sagar-khanna]

Describe the bug
We have HAProxy setup between the datadog agents and datadoghq which is using a self-signed certificate.
At the moment there is no provision on this line given below to pass OpenSSL::SSL::VERIFY_NONE or something similar to handle self-signed certificates in case of HAProxy or similar:

dogapi-rb/lib/dogapi/common.rb

Line 99 in 9ccd737

connection = Net::HTTP

Please note: The root CA is already installed at the global os level.
Raising this issue so we can add support to handle or ignore self-signed certificates in legitimate cases by either reading a chef attribute or using the datadog.yaml config (skip_ssl_validation: true) or something similar to make it work.

Label the issue properly.

• Add severity/ label.
• Add documentation label if this issue is related to documentation changes.

To Reproduce
Steps to reproduce the behavior:

1. Configure env such that agents talk to HAProxy to get to datadoghq
2. Use Chef (or similar) and add datadog:dd-handler recipe to the host's run_list
3. Observe the error at the end of a chef-client run.

Expected behavior
It should submit metrics to Datadog

Screenshots
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Environment and Versions (please complete the following information):
As per steps to reproduce section above.

Additional context
Add any other context about the problem here.