Fix default log level to a valid value

Fixes start failure under mcollective 2.3.x:

    /usr/lib/ruby/site_ruby/1.8/mcollective/logger/base.rb:26:in `>=': comparison of Fixnum with nil failed (ArgumentError)
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/logger/base.rb:26:in `should_log?'
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/log.rb:52:in `config_and_check_level'
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/log.rb:106:in `log'
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/log.rb:36:in `error'
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/pluginmanager.rb:171:in `loadclass'
    	from /usr/lib/ruby/site_ruby/1.8/mcollective/config.rb:142:in `loadconfig'
    	from /usr/sbin/mcollectived:29