Use Common.Logging 2.1.0 Instead of Common.Logging 2.2.0

Not sure why Common.Logging was upgraded from 2.1 to 2.2. A nuget package for Common.Logging.Log4Net that's compatible with Common.Logging 2.2.0 hasn't been published yet. I filed an [issue](https://github.com/net-commons/common-logging/issues/48) at the project's GitHub repo. In the meantime reverting back to version 2.1.2 so internal apps that use Common.Logging.Log4Net can upgrade to the latest version of the C# SDK.