rpc: further constrain the libevent workaround

The bug was introduced in 2.1.6-beta, versions before that don't need the
workaround.

src/httpserver.cpp

@@ -241,7 +241,7 @@ static std::string RequestMethodString(HTTPRequest::RequestMethod m)
 static void http_request_cb(struct evhttp_request* req, void* arg)
 {
     // Disable reading to work around a libevent bug, fixed in 2.2.0.
-    if (event_get_version_number() < 0x02020001) {
+    if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
         evhttp_connection* conn = evhttp_request_get_connection(req);
         if (conn) {
             bufferevent* bev = evhttp_connection_get_bufferevent(conn);
@@ -617,7 +617,7 @@ void HTTPRequest::WriteReply(int nStatus, const std::string& strReply)
         evhttp_send_reply(req_copy, nStatus, nullptr, nullptr);
         // Re-enable reading from the socket. This is the second part of the libevent
         // workaround above.
-        if (event_get_version_number() < 0x02020001) {
+        if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02020001) {
             evhttp_connection* conn = evhttp_request_get_connection(req_copy);
             if (conn) {
                 bufferevent* bev = evhttp_connection_get_bufferevent(conn);