If trusty, use older version of qemu

Fixes #10319
Signed-off-by: Warren Usui <warren.usui@inktank.com>
It coule be replaced by the **v2.2.0-rc** tag for clarity 
<pre>
$ git rev-parse v2.2.0-rc3^{}
2528043f1f299e0e88cb026f1ca7c40bbb4e1f80
</pre>