wget-log file created despite -q when run in background with &

== Steps to reproduce ==
`wget -q https://www.google.com/ &`

== What happens ==
wget says it's "Redirecting output to 'wget-log'" and creates an empty wget-log file in the current directory.

== What I expect to happen ==
No wget-log file to be created.

== Details ==
Wget has a -b (--background) option, for which the man page says: "If no output file is specified via the -o, output is redirected to wget-log." There's also the -q (--quiet) option, for which the man page says: "Turn off Wget's output."

When both are given, wget goes to background, and no wget-log gets created, as expected.

When only -b is given, wget goes to background, and creates wget-log, also as expected.

When only -q is given, wget runs in the foreground, and no wget-log is created, still as expected.

When only -q is given, but & is added to the end of the command line, wget goes to background, but also creates wget-log, which I find unexpected (and inconsistent).

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: wget 1.19.4-1ubuntu2
ProcVersionSignature: Ubuntu 4.15.0-15.16-generic 4.15.15
Uname: Linux 4.15.0-15-generic x86_64
ApportVersion: 2.20.9-0ubuntu5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Fri Apr 20 14:56:17 2018
InstallationDate: Installed on 2016-10-13 (553 days ago)
InstallationMedia: Ubuntu-Server 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fi_FI.UTF-8
 SHELL=/bin/bash
SourcePackage: wget
UpgradeStatus: No upgrade log present (probably fresh install)