client: increase read buffer size

Receiving large replies with 8kb buffer size is painfully slow.

Change-Id: Ife4a439d01153c60e8fd96d2c7f2874918fb4012
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/37838
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Reviewed-by: Georg Brandl <g.brandl@fz-juelich.de>

frappy/lib/asynconn.py

@@ -212,7 +212,7 @@ class AsynTcp(AsynConn):
         or bytes received within 1 sec
         """
         try:
-            data = self.connection.recv(8192)
+            data = self.connection.recv(1024*1024)
             if data:
                 return data
         except (socket.timeout, TimeoutError):