src: resolve issues reported by coverity

The specific issues raised by Coverity are:

** CID 182716:  Control flow issues  (DEADCODE)
/src/node_file.cc: 1192
>>> CID 182716:  Control flow issues  (DEADCODE)
>>> Execution cannot reach this statement:
    "args->GetReturnValue().Set(...".

** CID 182715:  Uninitialized members  (UNINIT_CTOR)
/src/node_file.h: 29
>>> CID 182715:  Uninitialized members  (UNINIT_CTOR)
>>> Non-static class member "syscall_" is not initialized in this
    constructor nor in any functions that it calls.

PR-URL: https://github.com/nodejs/node/pull/18629


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>