Oqgraph tests fail on kvm-deb-trusty-ppc64le due to missing libjudy

The builder kvm-deb-xenial-ppc64le builds the Oqgraph package and installs it for tests.

It turns out that long time ago, rather than making libjudy a dependency, we pre-installed it on our install VMs, see MDEV-5432. So, installation doesn't fail, only later the library fails to be loaded due to

2017-05-09 12:59:31 70366832332416 [ERROR] Can't open shared library '/usr/lib/mysql/plugin/ha_oqgraph.so' (errno: 2, libJudy.so.1: cannot open shared object file: No such file or directory)

I assume there was a good reason for this, I don't know/don't remember what it was. If it still exists, then the library needs to be installed on the new VMs as well. Otherwise, the dependency should be added to the oqgraph package (then it will probably have to wait till 10.3).