tests|lib: remove assert.h includes

Only the igt core and non-test tools should have asserts to catch
internal errors, tests and helper libraries should all user igt_asert
instead.

Fix things up where assert instead of igt_assert was used.

One tiny step towards header sanity.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

lib/drmtest.h

@@ -31,7 +31,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <assert.h>
 #include <errno.h>
 #include <stdbool.h>
 #include <setjmp.h>