Trying to run viewporter-test with ASan leak checking,
weston-desktop-shell helper client reports many leaks, because the
compositor quits before the client can start. Hence the
wl_display_roundtrip() fails.
Clean up by calling display_destroy() when wl_display_roundtrip() fails.
It's late enough that all kinds of things may have been allocated, so a
special local tear-down path is not feasible.
To make that work, display_destroy() must handle many things that might
be NULL which normally aren't. Also display_create() needs to initialize
lists early enough so that cleaning them up works.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>