Enhance ServiceManager with socket unit names

Enhance ServiceManager with socket unit names

In case of socket activated services additional units responsible
for listening on sockets can be passed to ServiceManager constructor.

Starting, stopping and restarting a service can affect now not only
service unit but also socket units.

This enhancement is used for implementation of cynara restart methods
with and without restarting socket units.

Change-Id: I619c94d3fc75b398240e85cd39ae78e757e03f1a