More cleanup of ConnectionState.process_input
More cleanup of ConnectionState.process_input

vitaly-krugl/pika,zixiliuyue/pika,pika/pika,jstnlef/pika,reddec/pika,Zephor5/pika,vrtsystems/pika,skftn/pika,renshawbay/pika-python3,hugoxia/pika,fkarb/pika-python3,Tarsbot/pika,knowsis/pika,benjamin9999/pika,shinji-s/pika