Clean up automated test suite dependencies
It's been a long while since we cleaned up those deps, and it's probable that some can be removed.
One specific point:
libxslt1-dev is not available on Debian Sid, and supposedly is not needed since some of us have been running the automated test suite without it on Sid. We should test if it's not needed on Debian Jessie too. At the same time we should check the other dependencies that are not obviously required.
libxslt1-dev is not needed by the automated test suite.
I believe it was a dependency of libvirt at some point, but it isn't
any more. It was removed from Sid for a while, and some of us managed
to run tests just fine without it.
radvd is not needed by the automated test suite.
It was added as a dependency early on, when we depended on an
experimental libvirt, which might have needed it. The test suite runs
well for me without it, unsurprisingly (we don't use IPv6).
x11-apps is not needed by the automated test suite.
We used xwd for failure screenshots at one point, but now we use