MINOR: cli: warning on _getsocks when socket were closed

MINOR: cli: warning on _getsocks when socket were closed

The previous attempt was reverted because it would emit a warning when
the sockets are still in the process when a reload failed, so this was
an expected 2nd try.

This warning however, will be displayed if a new process successfully
get the previous sockets AND the sendable number of sockets is 0.

This way the user will be warned if he tried to get the sockets fromt
the wrong process.