hydra-send-stats: Keep track of the number of machines

Dependencies

• [2] A2GL5FOZ Moar stats
• [*] DODOGD7M Send queue runner stats to statsd

Change contents

• edit in src/script/hydra-send-stats at line 51
  [2.1583]

  [4.1831]
  +

  + gauge("hydra.queue.machines.total", scalar(keys %{$json->{machines}}));

  + gauge("hydra.queue.machines.in_use", scalar(grep { $_->{currentJobs} > 0 } (values %{$json->{machines}})));