tests: shell: add test case for interval set with timeout and aborted transaction

tests: shell: add test case for interval set with timeout and aborted transaction

Add a regression test for rbtree+bsearch getting out-of-sync in
nf-next kernel.

This covers the syzkaller reproducer from
https://syzkaller.appspot.com/bug?extid=d417922a3e7935517ef6
which triggers abort with earlier gc at insert time and additional corner
case where transaction passes without recording a relevant change in the set
(i.e. no call to either abort or commit).

This test passes even on buggy kernels unless KASAN is enabled.

Signed-off-by: Florian Westphal <fw@strlen.de>