Fix so EOS are delivered to sessions in the pool (#7828)

(cherry picked from commit 9a7742a)

Author: shinrich

proxy/PoolableSession.h

@@ -83,6 +83,8 @@ class PoolableSession : public ProxySession
 
   void set_netvc(NetVConnection *newvc);
 
+  virtual IOBufferReader *get_reader() = 0;
+
 private:
   // Sessions become if authentication headers
   //  are sent over them

proxy/http/Http1ClientSession.cc

@@ -467,7 +467,7 @@ Http1ClientSession::attach_server_session(PoolableSession *ssession, bool transa
     //  have it call the client session back.  This IO also prevent
     //  the server net conneciton from calling back a dead sm
     SET_HANDLER(&Http1ClientSession::state_keep_alive);
-    slave_ka_vio = ssession->do_io_read(this, 0, nullptr);
+    slave_ka_vio = ssession->do_io_read(this, INT64_MAX, ssession->get_reader()->mbuf);
     ink_assert(slave_ka_vio != ka_vio);
 
     // Transfer control of the write side as well

proxy/http/Http1ServerSession.h

@@ -76,7 +76,7 @@ class Http1ServerSession : public PoolableSession
   void start() override;
 
   void enable_outbound_connection_tracking(OutboundConnTrack::Group *group);
-  IOBufferReader *get_reader();
+  IOBufferReader *get_reader() override;
   void attach_hostname(const char *hostname);
   IpEndpoint const &get_server_ip() const;
 

proxy/http/HttpSessionManager.cc

@@ -206,7 +206,9 @@ ServerSessionPool::releaseSession(PoolableSession *ss)
   //  if it closes on us.  We will get called back in the
   //  continuation for this bucket, ensuring we have the lock
   //  to remove the connection from our lists
-  ss->do_io_read(this, 0, nullptr);
+  //  Actually need to have a buffer here, otherwise the vc is
+  //  disabled
+  ss->do_io_read(this, INT64_MAX, ss->get_reader()->mbuf);
 
   // Transfer control of the write side as well
   ss->do_io_write(this, 0, nullptr);