Refused connection, validation failed for Amazon Provider http proxy

Issue

• Edited http proxy in the web UI via Settings => Configuration => Zones => Server => Advanced Tab
• But when trying to add Amazon Provider, getting the following errors in the logs:

[----] W, [2016-08-10T16:01:52.406435 #4766:11022a4]  WARN -- : MIQ(ManageIQ::Providers::Amazon::CloudManager#authentication_check_no_validation) type: ["default"] for [] [AWS] Validation failed: error, Unexpected response returned from system: Connection refused - connect(2) for "<DomainName\>" port 443