update thrift to use managed connection

Summary:
Use the new managed connection code in folly.  Cleans things up a fair bit

The only catch was the current ConnectionManager code uses raw pointers, thrift expects shared_ptr so the request object can keep the channel around until the requests are finished

Test Plan: fbconfig -r thrift/lib/cpp2; fbmake runtests

Reviewed By: afrind@fb.com

Subscribers: trunkagent, njormrod, doug, fugalh, alandau, bmatheny, dcsommer, afrind

FB internal diff: D1519923

Tasks: 5002343

folly/experimental/wangle/ConnectionManager.h

@@ -121,6 +121,15 @@ class ConnectionManager: public folly::DelayedDestruction {
 
   size_t getNumConnections() const { return conns_.size(); }
 
+  template <typename F>
+  void iterateConns(F func) {
+    auto it = conns_.begin();
+    while ( it != conns_.end()) {
+      func(&(*it));
+      it++;
+    }
+  }
+
  private:
   class CloseIdleConnsCallback :
       public folly::EventBase::LoopCallback,