With the completion of JENKINS-61337 a second HTTP engine has been introduced into the project. This is the NettyHttp engine which is the default in the Azure Java SDK. Thankfully they have abstracted their library well enough to allow other engines and also kindly implemented the OkHttp implementation as a separate libary.

https://github.com/Azure/azure-sdk-for-java/wiki/HTTP-clients

Update the project to use the OkHttp engine for Azure so that we can make use of the shared infrastructure already in place.

Acceptance Criteria:

1. All HTTP interaction is done via OkHttp.
2. Clean up any old Netty related code.