Update amprupdate.py

RouterOS 6.22 activates keepalive by default with 10 seconds interval, resulting in unnecessary packets being sent to remote endpoints and eventually interface flapping due to missing support for keepalive packets.
The clamp-tcp-mss allows to automatically clamp the TCP MSS, so there no need for a Firewall entry anymore.
Merge pull request #5 from mstorck/patch-4

Update amprupdate.py to disable keepalive packets and clamp-tcp-mss=yes