Enabled debian services on ubuntu are always enabled

Right now, 'service: enabled' on ubuntu will call 'update-rc.d defaults' which
will not enable the service if rc.d symlinks already exist. debian services on
debian will call 'update-rc.d enable', this change makes ubuntu consistent with
debian
Merge pull request #18854 from kenatbasis/consistent-service-enable

Enabled debian services on ubuntu are always enabled