MINOR: init: check MODE_MWORKER before creating master CLI

MINOR: init: check MODE_MWORKER before creating master CLI

mworker_create_master_cli() creates MASTER proxy and allocates listeners,
which are attached to this proxy. It also creates a reload sockpair.

So, it's more appropriate to do the check, that we are in a MODE_MWORKER, if
master CLI settings were provided via command line, just after the config
parsing. And only then, if runtime mode and command line settings are
coherent, try to perform master-worker fork and try to create master CLI.