Updated dotnet-agent to fix attribute conflict and .NET pre-req

There was an attribute conflict between the dotnet-agent and java-agent recipes. Updated the attribute name on dotnet-agent to unique name.

Updated the Windows server agent and dotnet-agent installs to first check if .NET 4 is installed before trying to run ms_dotnet4 cookbook. Because of recommends we were getting errors with ms_dotnet4 not being in the run list but we already have .NET on the machine.