qemuTestDriverInit: Don't autopopulate qemu capabilities when initializing driver

qemuTestDriverInit: Don't autopopulate qemu capabilities when initializing driver

In an effort to use strictly real capability testing all tests were
converted to do insertion of their own capabilities when required, thus
we don't need to popluate the capabilities. This will also promote using
proper capabilities based on what the test is trying to achieve.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>