Changes

jobs/ttcn3: io_uring: set memlock to unlimited

io_uring in the kernel memlocks a big amount of space with older
kernels, such as the kernel on host2-deb11build-ansible. It seemed to be
enough to increase it to 1 GiB. However now we see it failing again
with:

  failure during io_uring_queue_init(): Cannot allocate memory
  Aborted (core dumped)

Set it to unlimited to ensure that a low limit is not the reason we see
it failing. If it still happens after this, we probably need to make
sure that we don't run too many SUTs with io_uring in parallel on
jenkins nodes with older kernels.

Related: OS#6405
Change-Id: I39aaa2ed7d0310a12d0c4493a79ff46b2e7e2864