Properly catch SocketException when calling GetHostEntry

Using GetHostEntry instead of GetHostEntryAsync + Wait means the `SocketException` is no longer wrapped inside an `AggregateException`.

Also simplify catching the the `AggregateException` in the .NET Standard 1.6 code path by using `GetBaseException()`.

Ductus.FluentDocker/Extensions/CommandExtensions.cs

@@ -161,23 +161,33 @@ public static bool IsEmulatedNative()
     }
 
 
+#if NETSTANDARD1_6
     public static bool IsDockerDnsAvailable()
     {
       try
       {
-#if NETSTANDARD1_6
         Dns.GetHostEntryAsync("host.docker.internal").Wait();
+        return true;
+      }
+      catch (Exception ex) when (ex.GetBaseException() is SocketException)
+      {
+        return false;
+      }
+    }
 #else
+    public static bool IsDockerDnsAvailable()
+    {
+      try
+      {
         Dns.GetHostEntry("host.docker.internal");
-#endif
         return true;
       }
-      catch (AggregateException ex)
-        when (ex.InnerExceptions.Count == 1 && ex.InnerExceptions[0] is SocketException)
+      catch (SocketException)
       {
         return false;
       }
     }
+#endif
 
     public static bool IsNative()
     {