chore: Remove System.Net.Http reference on .NET Framework. Resolves #2750 (#2751)

* chore: Remove System.Net.Http reference on .NET Framework

* Fix unit test

Author: chynesNR

src/Agent/NewRelic/Agent/Core/DataTransport/ConnectionManager.cs

@@ -10,7 +10,9 @@
 using System.IO;
 using System.Linq;
 using System.Net;
+#if !NETFRAMEWORK
 using System.Net.Http;
+#endif
 using System.Net.Sockets;
 
 namespace NewRelic.Agent.Core.DataTransport
@@ -107,12 +109,14 @@ private void Connect()
             {
                 HandleHttpErrorResponse(ex);
             }
+#if !NETFRAMEWORK // Only available in System.Net.Http
             // Occurs when the agent is unable to connect to APM. The request failed due to an underlying
             // issue such as network connectivity, DNS failure, server certificate validation or timeout.
             catch (HttpRequestException)
             {
                 ScheduleRestart();
             }
+#endif
             // Occurs when the agent connects to APM but the connection gets aborted by the collector
             catch (SocketException)
             {
@@ -168,7 +172,7 @@ public T SendDataRequest<T>(string method, params object[] data)
             }
         }
 
-        #endregion Synchronized methods
+#endregion Synchronized methods
 
         #region Helper methods
 

tests/Agent/UnitTests/Core.UnitTest/DataTransport/ConnectionManagerTests.cs

@@ -85,10 +85,12 @@ public void AttemptAutoStart_SchedulesConnectAsynchronously_IfAutoStartIsOnAndSy
         [Test]
         [TestCase("ForceRestartException")]
         [TestCase("HttpException")]
-        [TestCase("HttpRequestException")]
         [TestCase("SocketException")]
         [TestCase("IOException")]
         [TestCase("OperationCanceledException")]
+#if !NETFRAMEWORK
+        [TestCase("HttpRequestException")]
+#endif
         public void AttemptAutoStart_SchedulesReconnect_IfCertainExceptionOccurs(string execeptionType)
         {
             Exception ex = null;