Simplify is_service_enabled
Simplify is_service_enabled

Remove service_name argument from the is_service_enabled function.
The argument is unused and complicates the function's logic.

Change-Id: I1ac8a037bd7908ef1101d5fec359a8fe0e16e24a

coreycb/horizon,redhat-cip/horizon,gerrive/horizon,redhat-openstack/horizon,gerrive/horizon,redhat-cip/horizon,maestro-hybrid-cloud/horizon,coreycb/horizon,BiznetGIO/horizon,Mirantis/mos-horizon,dan1/horizon-x509,bac/horizon,Mirantis/mos-horizon,philoniare/horizon,openstack/horizon,gerrive/horizon,bac/horizon,noironetworks/horizon,openstack/horizon,philoniare/horizon,anthonydillon/horizon,noironetworks/horizon,Mirantis/mos-horizon,openstack/horizon,NeCTAR-RC/horizon,Tesora/tesora-horizon,Tesora/tesora-horizon,bigswitch/horizon,Tesora/tesora-horizon,dan1/horizon-x509,ChameleonCloud/horizon,Mirantis/mos-horizon,bigswitch/horizon,maestro-hybrid-cloud/horizon,noironetworks/horizon,redhat-openstack/horizon,yeming233/horizon,idjaw/horizon,coreycb/horizon,coreycb/horizon,bac/horizon,yeming233/horizon,Tesora/tesora-horizon,sandvine/horizon,redhat-openstack/horizon,dan1/horizon-x509,davidcusatis/horizon,openstack/horizon,saydulk/horizon,BiznetGIO/horizon,wolverineav/horizon,yeming233/horizon,django-leonardo/horizon,sandvine/horizon,davidcusatis/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,sandvine/horizon,dan1/horizon-x509,sandvine/horizon,ChameleonCloud/horizon,BiznetGIO/horizon,django-leonardo/horizon,davidcusatis/horizon,anthonydillon/horizon,gerrive/horizon,anthonydillon/horizon,noironetworks/horizon,redhat-cip/horizon,wolverineav/horizon,django-leonardo/horizon,NeCTAR-RC/horizon,idjaw/horizon,idjaw/horizon,davidcusatis/horizon,maestro-hybrid-cloud/horizon,philoniare/horizon,bac/horizon,yeming233/horizon,philoniare/horizon,wolverineav/horizon,NeCTAR-RC/horizon,redhat-cip/horizon,idjaw/horizon,anthonydillon/horizon,NeCTAR-RC/horizon,saydulk/horizon,django-leonardo/horizon,saydulk/horizon,maestro-hybrid-cloud/horizon,wolverineav/horizon,saydulk/horizon,redhat-openstack/horizon,BiznetGIO/horizon,bigswitch/horizon,bigswitch/horizon