engine: refactor CollectVdsNetworkDataVDSCommand

Refactor CollectVdsNetworkDataVDSCommand: extract the network topology
persistence logic into its own class with non-static methods.

Change-Id: I798abe6597c06df873ac94f61981ff1dccc07bc8
Signed-off-by: Yevgeny Zaspitsky <yzaspits@redhat.com>
Signed-off-by: Moti Asayag <masayag@redhat.com>