Set service name correctly when using Azure Pipelines urls (#1846)

The previous service naming logic used the instance's subdomain. When an
Azure Pipelines url was provided, "dev" was always used. Now, the instance
name will be obtained from the url's path if an Azure Pipelines url is
provided.

Resolves #1841

src/Agent.Listener/Configuration/ServiceControlManager.cs

@@ -35,7 +35,18 @@ public void CalculateServiceName(AgentSettings settings, string serviceNamePatte
             serviceName = string.Empty;
             serviceDisplayName = string.Empty;
 
-            string accountName = new Uri(settings.ServerUrl).Host.Split('.').FirstOrDefault();
+            Uri accountUri = new Uri(settings.ServerUrl);
+            string accountName = string.Empty;
+
+            if (accountUri.Host.Equals("dev.azure.com", StringComparison.OrdinalIgnoreCase))
+            {
+                accountName = accountUri.AbsolutePath.Split('/', StringSplitOptions.RemoveEmptyEntries).FirstOrDefault();
+            }
+            else
+            {
+                accountName = accountUri.Host.Split('.').FirstOrDefault();
+            }
+
             if (string.IsNullOrEmpty(accountName))
             {
                 throw new InvalidOperationException(StringUtil.Loc("CannotFindHostName", settings.ServerUrl));