The only reason why we have both weston_compositor_tear_down() and
weston_compositor_destroy() is that the only we had to destroy
the log context was keeping weston_compositor alive and calling
weston_log_ctx_compositor_destroy().
After commit "weston-log: replace weston_log_ctx_compositor_destroy()
by weston_log_ctx_destroy()", it's not necessary to keep a zombie
weston_compositor just to be able to call
weston_log_ctx_compositor_destroy().
Fold weston_compositor_tear_down() into weston_compositor_destroy(),
as this split is useless now.
Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>