Fixing blocking system call to async mode

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
Change-Id: Id81db4d512b5ea1222a145dc2b9e9907e8b0f084
diff --git a/include/vm_websocket.hpp b/include/vm_websocket.hpp
index 188bcf2..89270d9 100644
--- a/include/vm_websocket.hpp
+++ b/include/vm_websocket.hpp
@@ -46,8 +46,10 @@
         int rc = kill(proxy.id(), SIGTERM);
         if (rc != 0)
         {
+            BMCWEB_LOG_ERROR << "Failed to terminate nbd-proxy: " << errno;
             return;
         }
+
         proxy.wait();
     }