Fix for rc-status not showing puppet when puppet is run as a service

/bin/rc-status doesn't show the service specified in the environment
variable "RC_SVCNAME", which when puppet is started as a service is set
to "puppet".

Updated to use "has_command" instead of ENV.delete
Ensure that openrc service provider wipes RC_SVCNAME variable
Merge branch 'pull-1646'

This closes GH-1646