Always inject PacketSocketFactory in FakePortAllocator

This CL removes the use of the rtc::Thread::socketserver() method
in one place.

Bug: webrtc:13145
Change-Id: I1a1b2501450788263d5280c43e4328ade46f4146
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/263320
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Daniel.L (Byoungchan) Lee <daniel.l@hpcnt.com>
Cr-Commit-Position: refs/heads/main@{#37340}
diff --git a/pc/rtc_stats_integrationtest.cc b/pc/rtc_stats_integrationtest.cc
index 9d2328a..eccc226 100644
--- a/pc/rtc_stats_integrationtest.cc
+++ b/pc/rtc_stats_integrationtest.cc
@@ -111,9 +111,11 @@
     RTC_CHECK(worker_thread_->Start());
 
     caller_ = rtc::make_ref_counted<PeerConnectionTestWrapper>(
-        "caller", network_thread_.get(), worker_thread_.get());
+        "caller", &virtual_socket_server_, network_thread_.get(),
+        worker_thread_.get());
     callee_ = rtc::make_ref_counted<PeerConnectionTestWrapper>(
-        "callee", network_thread_.get(), worker_thread_.get());
+        "callee", &virtual_socket_server_, network_thread_.get(),
+        worker_thread_.get());
   }
 
   void StartCall() {