tests: defer face deallocation in Face/TestTcp and Face/TestWebSocket

Deallocating face immediately at face closing would cause a Signal object
in the transport to be destructed during its execution, which is disallowed.

refs #3322

Change-Id: I4eb23f34305cfecf7d2122e94454a97353707818

tests/daemon/face/tcp.t.cpp

@@ -171,8 +171,10 @@ public:
   void
   face1_onFail()
   {
-    face1.reset();
-    limitedIo.afterOp();
+    g_io.post([this] {
+      face1.reset();
+      limitedIo.afterOp();
+    });
   }
 
   void
@@ -214,8 +216,10 @@ public:
   void
   face2_onFail()
   {
-    face2.reset();
-    limitedIo.afterOp();
+    g_io.post([this] {
+      face2.reset();
+      limitedIo.afterOp();
+    });
   }
 
   void

tests/daemon/face/websocket.t.cpp

@@ -112,8 +112,10 @@ public:
   void
   face1_onFail()
   {
-    face1.reset();
-    limitedIo.afterOp();
+    g_io.post([this] {
+      face1.reset();
+      limitedIo.afterOp();
+    });
   }
 
   void