Simplify openvswitch -> ovn directory change

[fprzewozny]

Please provide some sort of parameter switch, that could be used for selecting general service name (currently default openvswitch, and ovn). In environment that uses ovn directory names, proper configuration require dozen of parameters, with 'name' switch, it could be done with just one.

Instead of this:
ovn-exporter -database.northbound.file.data.path /var/lib/ovn/ovnnb_db.db -database.northbound.file.log.path /var/log/ovn/ovsdb-server-nb.log -database.northbound.file.pid.path /run/ovn/ovnnb_db.pid -database.northbound.socket.control unix:/run/ovn/ovnnb_db.ctl -database.northbound.socket.remote unix:/run/ovn/ovnnb_db.sock -database.southbound.file.data.path /var/lib/ovn/ovnsb_db.db -database.southbound.file.log.path /var/log/ovn/ovsdb-server-sb.log -database.southbound.file.pid.path /run/ovn/ovnsb_db.pid -database.southbound.socket.control unix:/run/ovn/ovnsb_db.ctl -database.southbound.socket.remote unix:/run/ovn/ovnsb_db.sock -service.ovn.northd.file.log.path /var/log/ovn/ovn-northd.log -service.ovn.northd.file.pid.path /run/ovn/ovn-northd.pid
We could have something like that:
ovn-exporter -system.directory.name ovn