FIX: Calculate segment_id for VLAN mode

PRD-2130
FIX: more strong order for start ovs-agent-service

+typo
FIX: private_interface not always present in config
remove unnided variables
Merge pull request #693 from xenolog/PRD-2130

FIX: Calculate segment_id for VLAN mode
Merge pull request #694 from xenolog/PRD-2172

FIX: private_interface not always present in config
Merge pull request #696 from xenolog/PRD-2149

remove unnided variables from Horizon config