commands/test: Fix error in recursion depth calculation

commands/test: Fix error in recursion depth calculation

The commit c68b7d236 (commands/test: Stack overflow due to unlimited
recursion depth) added recursion depth tests to the test command. But in
the error case it decrements the pointer to the depth value instead of
the value itself. Fix it.

Fixes: c68b7d236 (commands/test: Stack overflow due to unlimited recursion depth)
Signed-off-by: Thomas Frauendorfer | Miray Software <tf@miray.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>