Increase the Orchestrator's default connection limit (#677)

The Orchestrator used the default connection limit of 2 per server. The Orchestrator processes messages in parallel, each of which may be downloading/uploading large files.

Part of NuGet/NuGetGallery#6624

src/NuGet.Services.Validation.Orchestrator/Job.cs

@@ -47,6 +47,11 @@ namespace NuGet.Services.Validation.Orchestrator
 {
     public class Job : JobBase
     {
+        /// <summary>
+        /// The maximum number of concurrent connections that can be established to a single server.
+        /// </summary>
+        private const int MaximumConnectionsPerServer = 64;
+
         private const string ConfigurationArgument = "Configuration";
         private const string ValidateArgument = "Validate";
 
@@ -93,6 +98,8 @@ public class Job : JobBase
 
         public override void Init(IServiceContainer serviceContainer, IDictionary<string, string> jobArgsDictionary)
         {
+            ServicePointManager.DefaultConnectionLimit = MaximumConnectionsPerServer;
+
             var configurationFilename = JobConfigurationManager.GetArgument(jobArgsDictionary, ConfigurationArgument);
             _validateOnly = JobConfigurationManager.TryGetBoolArgument(jobArgsDictionary, ValidateArgument, defaultValue: false);