Update servicegroup.rb
Update servicegroup.rb

Fixing the undefined method `create' for Nagios::Servicegroup:Class in #347
bitmonk/chef-nagios,firebase/nagios,aaronkvanmeerten/nagios,Piousbox-cookbooks/nagios,OpenGov/nagios,schubergphilis/nagios,firebase/nagios,aaronkvanmeerten/nagios,bitmonk/chef-nagios,spudnic/nagios,spudnic/nagios,earzur/nagios,ovaistariq/nagios,bitmonk/chef-nagios,firebase/nagios,JulianNL/nagios,spudnic/nagios,bitmonk/chef-nagios,aaronkvanmeerten/nagios,ovaistariq/nagios,earzur/nagios,JulianNL/nagios,JulianNL/nagios,Piousbox-cookbooks/nagios,JulianNL/nagios,ovaistariq/nagios,OpenGov/nagios,schubergphilis/nagios,polamjag/nagios,OpenGov/nagios,mrlamroger/nagios,polamjag/nagios,spudnic/nagios,mrlamroger/nagios,earzur/nagios,Piousbox-cookbooks/nagios,OpenGov/nagios,polamjag/nagios,schubergphilis/nagios,firebase/nagios,Piousbox-cookbooks/nagios,mrlamroger/nagios,mrlamroger/nagios