If Tarantool server segfaults when a test is
running, it used to hand in <defunct> state,
since there was no wait() call in the parent
to collect child process state. All file descriptors,
as well as open sockets, of a <defunct> process were
left open. This lead to the test runner cycling
in an infinite loop in recv() from the server,
and the whole test suite to, ultimately, hanging
in a busy wait.

This looks more like a bug in python pexpect,
but install a SIGCHLD handler to work it around,
and collect child data immediately as soon as
child terminates.