tests: Don't use ptrace detach stopped trick. Raise can return.

On older kernels the ptrace detach stop trick doesn't work reliably.
Just keep the child processes attached and stopped during the tests,
dwfl_linux_proc_attach will handle that fine now. Also on older kernels
raise would sometimes return anyway and cause a spurious assert. Just
ignore it.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
4 files changed