Ubuntu Software sign in menu needs UI work

[Jeremy Bícha]

See the attached screenshot.

1. In my opinion, a menu shouldn't show Sign Out (even if greyed out) at the same time as it shows Sign In.

There are a few other usability issues. Let me know if you want separate bugs.

2. I am already logged in to Ubuntu Single Sign-On in GNOME Online Accounts, set up with Ubuntu Welcome.

3. The same credentials work for both the Snap Store and Ubuntu One so I think there shouldn't be separate sign in buttons.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: gnome-software 3.29.92-0ubuntu2
ProcVersionSignature: Ubuntu 4.17.0-9.10-generic 4.17.17
Uname: Linux 4.17.0-9-generic x86_64
ApportVersion: 2.20.10-0ubuntu9
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Sep 4 22:26:58 2018
InstallationDate: Installed on 2017-10-13 (327 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Beta amd64 (20171012)
InstalledPlugins:
 gnome-software-plugin-flatpak N/A
 gnome-software-plugin-limba N/A
 gnome-software-plugin-snap 3.29.92-0ubuntu2
SourcePackage: gnome-software
UpgradeStatus: Upgraded to cosmic on 2018-08-23 (12 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.