Extend the coredump_socket and coredump_socket_protocol selftests to verify
that the field coredump_code is set as expected in struct pidfd_info.
Signed-off-by: Emanuele Rocca <emanuele.rocca@arm.com>
Link: https://patch.msgid.link/acE6Eyuv2MM75pmk@NH27D9T0LF
Signed-off-by: Christian Brauner <brauner@kernel.org>