unix: don't use req->loop in uv__fs_copyfile()
unix: don't use req->loop in uv__fs_copyfile()

Pass NULL instead of req->loop to the various libuv functions
called from uv__fs_copyfile().

Refs: https://github.com/libuv/libuv/pull/1494
PR-URL: https://github.com/libuv/libuv/pull/1504
Reviewed-By: Ben Noordhuis <59bd0a3ff43b32849b319e645d4798d8a5d1e889@bnoordhuis.nl>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso