[SRU] Update ubuntu-kylin-software-center to 0.2.9.6

ubuntu-kylin-software-center has made a few bug fixes, the major one being the adoption of a more professional UI, which is crucial for OEM pre-load.

[Impact]
These bugs are fixed from 0.2.9.2 to 0.2.9.6:
  - bug 1296054: the screenshot of the main window has narrow edging of background
  - bug 1304264: UI is not professional
  - bug 1307275: rank in main window does not show completely
  - bug 1306137: T-shirt icon does nothing
  - bug 1307331: can not install apps if cancel or delay password input
  - bug 1309900: search entry is covered by search result view
  - bug 1307280: restart func would be done by calling os.execv

[Test Case]
 These test cases can help to confirm the bug:
  - case for bug 1296054
     * run the software center and catch the screenshot of the main window, there will be a narrow edging of background.
  - case for bug 1304264
     * many users suggest to change the UI because the former one seems not so professional.
  - case for bug 1307275
     * the rank view in main window is not showed completely on a low resolution desktop, such as in virtual machine.
  - case for bug 1306137
     * the T-shirt icon has no effect.
  - case for bug 1307331
     * run the software center and click "install" button of some app. Then the authentication dialog will be prompted for the user to input password. choose "cancel" or input password in one minute, the installation does not start, but task item in "task view" show "in preparation...".
  - case for bug 1309900
     * run the software center and input a key word in search entry. the results are showed in search view and the search entry is covered. Then the user can not find search entry after that.
  - case for bug 1307280
     * change the restart function by os.execv instead of spawning a new process according to slangasek's suggestion.

[Regression Potential]
 The above updates are constrained inside the software center. The potential risks are showed as following:
  - the UI changes, including updates for bugs 1296054/1304264/1307275/1306137/1309900, mainly modify the UI related codes which have no effect on software functions. However, the potential incomplete replace of UI components for bug 1304264 may cause part of the interface doesn't look good with the rest, although no such issue from our testing.
  - the updates of policykit authentication for bug 1307331 just add exception check to prevent backend crash and do not modify other procedures.
  - the change for bug 1307280 just replace the function for starting a process. This operation will only be called after the software center itself updated.