Support for proxy in datastore drivers

[OpenNebulaSupport]

Description Allow datastore drivers to have an http proxy set in a configuration file. Without this, the marketplace drivers can only monitor de appliances in the marketplaces. They will fail when importing them into a datastore because the datastore driver does not share the configuration with the marketplace.

Use case Importing marketplace appliances

Interface Changes None

Additional Context Configuration should be done similar to the transfer manager driver configuration. A dsrc file should hold the configuration.

Progress Status

• [ ] Code committed
• [ ] Testing - QA
• [ ] Documentation (Release notes - resolved issues, compatibility, known issues)