Allow .reset on MultiLogger

[dpca]

I'm using a MultiLogger and tried setting up the Phusion Passenger cleanup as specified:

::PhusionPassenger.on_event(:starting_worker_process) do |forked|
  Rails.logger.reset
end

but ran into the following error:

wrong number of arguments (given 1, expected 0) (ArgumentError)
  /usr/local/rvm/gems/ruby-2.5.3/gems/logstash-logger-0.26.1/lib/logstash-logger/logger.rb:23:in `reset'
  /usr/local/rvm/gems/ruby-2.5.3/gems/logstash-logger-0.26.1/lib/logstash-logger/multi_logger.rb:73:in `block in method_missing'
  /usr/local/rvm/gems/ruby-2.5.3/gems/logstash-logger-0.26.1/lib/logstash-logger/multi_logger.rb:71:in `each'
  /usr/local/rvm/gems/ruby-2.5.3/gems/logstash-logger-0.26.1/lib/logstash-logger/multi_logger.rb:71:in `method_missing'

I dug a bit and think this PR should fix it. Thanks!