[server] some refactoring of the server config file parser
[server] some refactoring of the server config file parser

* Use the already existing helper function more often
* Fix incorrect checks for missing config keys

luckielordie/conan,memsharded/conan,birsoyo/conan,memsharded/conan,memsharded/conan,memsharded/conan,conan-io/conan,conan-io/conan,birsoyo/conan,luckielordie/conan,conan-io/conan