NetworkPkg: Handle wait exit on poll failure

`EfiDhcp4Start()` would spin forever if `DhcpSb->IoStatus` is not
updated from `EFI_ALREADY_STARTED`.

This change captures the poll status (instead of ignoring it) and
break out on failures so scenarios like unplug/media-loss return an
error instead of hanging.

Signed-off-by: Michael Kubacki <[email protected]>

Author: makubacki

NetworkPkg/Dhcp4Dxe/Dhcp4Impl.c

@@ -824,7 +824,15 @@ EfiDhcp4Start (
 
   if (CompletionEvent == NULL) {
     while (DhcpSb->IoStatus == EFI_ALREADY_STARTED) {
-      DhcpSb->UdpIo->Protocol.Udp4->Poll (DhcpSb->UdpIo->Protocol.Udp4);
+      // MU_CHANGE [BEGIN] - Add Udp4 Polling break support
+      Status = DhcpSb->UdpIo->Protocol.Udp4->Poll (DhcpSb->UdpIo->Protocol.Udp4);
+      if (EFI_ERROR (Status)) {
+        // Break out if the NIC goes away or poll fails so we don't spin forever.
+        DhcpSb->IoStatus = Status;
+        break;
+      }
+
+      // MU_CHANGE [END] - Add Udp4 Polling break support
     }
 
     return DhcpSb->IoStatus;