FIX: Reopen sidekiq log files after rotation (PR #9429)

Unicorn uses the USR1 to indicate that log files should be reopened. This commit implements the same functionality for our forked sidekiq workers:

  • USR1 is intercepted in the unicorn master, and re-issued to all child processes
  • USR1 is trapped in the sidekiq processes, and Unicorn::Util.reopen_logs is used to re-open log files