Wrong input method is activated when using "Previous method" keyboard to switch.

[jeremy-list]

To replicate:
1. In the IBus configuration: add the following input methods to the list:
  1. US English
  2. Libpinyin or Pinyin (bug present for both)
  3. Russian
2. Make sure there are keyboard shortcuts for cycling between input methods
3. In another application: press the keyboard shortcut for "previous input method" until the status bar icon shows the pinyin input method
4. Type something.

Expected results:
There should be a character selection box allowing the user to select Chinese characters.

Actual results:
Cyrillic characters appear on the screen.

NB: I can only reproduce the bug if I use the "Previous method" shortcut. If using the "Next method" shortcut I get the correct behaviour.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ibus 1.5.11-1ubuntu2
ProcVersionSignature: Ubuntu 4.10.0-27.30~16.04.2-generic 4.10.17
Uname: Linux 4.10.0-27-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Jul 26 14:03:04 2017
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/ibus-daemon
InstallationDate: Installed on 2017-07-22 (3 days ago)
InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
SourcePackage: ibus
UpgradeStatus: No upgrade log present (probably fresh install)