tests: rename xwayland test

tests: rename xwayland test

If the test is named xwayland.weston, then the automake test harness
keys it off xwayland.log. Making xwayland.log runs the test.
The test harness has implicit rules to create a %.log from all of
%$TEST_EXTENSIONS. So we have implicit rules to create %.log from %.la
and %.log from %.weston.

We also build xwayland.so, which produces xwayland.la.

When the test harness goes running the xwayland test, it ends up using
the %.la rule, which is wrong. It passes xwayland.la as the test name to
weston-tests-env, which then loads it as a plugin into Weston and waits
for Weston to exit. Which it never does.

Fix this by making the test have a different name than the Xwayland
plugin.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>