core: merge a few if blocks

arg_system == true and getpid() == 1 hold under the very same condition
this early in the main() function (this only changes later when we start
parsing command lines, where arg_system = true is set if users invoke us
in test mode even when getpid() != 1.

Hence, let's simplify things, and merge a couple of if branches and not
pretend they were orthogonal.