Bluepill doesn't honor stop_signals delays

[guss77]

When using stop signals to set up a multiple signals shutdown process with a delay between signals, then when issuing a stop command Bluepill does the first signal and then just terminates all the processes and exits.

The problem seems to be in process.rb, where if stop_signals are set, it starts a thread to handle the stop_signals, and then immediately calls kill_all_from_journal which basically just sends TERM to all processes.

A correct implementation of this is required to handle graceful shutdown of processes with a long shutdown process, such as a resque worker.