tests: replace --enable-docker with --enable-root-make-check

The --enable-docker logic was that each test that needs privileges to
run uses a container to do so. The problem with this approach and
make -j8 check is that such tests compete for a single container.

The --enable-root-make-check activates tests that require privileges and
assume it is ok to use sudo to acquire privileges. The decision to run
in a container is then taken by the caller who will run something like:

   docker-tests.sh ./configure --enable-root-make-check
   docker-tests.sh make -j8 check

Signed-off-by: Loic Dachary <ldachary@redhat.com>
tests: run-make-check.sh arguments are passed to configure

All run-make-check.sh arguments are transparently given to the configure
command. For instance:

    run-make-check.sh --enable-root-make-check

implies

    ./configure --enable-root-make-check

Signed-off-by: Loic Dachary <ldachary@redhat.com>
tests: helpers to run make check in containers

Add scripts that run make check in a container for a given operating
system version. They are a little more than oneliners and serve two
purposes:

  * help new developers who do not have to figure out which options
    should be used

  * run make check in containers in parallel with make -j2

Signed-off-by: Loic Dachary <ldachary@redhat.com>
tests: add xmlstarlet in containers

It can be removed once https://github.com/ceph/ceph/pull/3228 is merged
and xmlstarlet is found in ceph.spec.in and debian/control.

Signed-off-by: Loic Dachary <ldachary@redhat.com>