shared: Add defensive measures to array handling

shared: Add defensive measures to array handling

- Make sure that SIZE_MAX boundaries are never crossed
- Clear pointer address in struct during array_free_array
- Do nothing if array_pop is called with empty array

Also added test case for pop behavior and extended tests with
more checks.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/68
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>