ANDROID: make memory initialization tests panic on failure

This is a patch specific to android-common-4.14 where lib/test_meminit.c
and lib/test_stackinit.c are built into the kernel.

Call panic() to make the test failures more visible.

Bug: 144999193

Change-Id: Iaa9459f4bf63753c5ac1cf51c9691bf62b3924e9
Signed-off-by: Alexander Potapenko <glider@google.com>