Php_grpc_bench: should enable production php.ini.

It is strongly recommended to use the production config for images used in production environments. Please see below. 
https://hub.docker.com/_/php

Then, the code below should be added to the docker file of php_grpc_bench.
`RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini""`