pidfd_send_signal02 assumes we can't send signal to pid 1

[richiejp]

The test assumes pid 1 is init and we can't send a signal to it. If we are in a pid namespace (e.g. a container) then pid 1 could be sh or even the LTP test and we can send signals to it.

Ideally the test would create a process which is explicitly forbidden from signalling another process instead of relying on system configuration.