Test disable dhcp
fixes for the rebase
Test disable dhcp

Added test Tempest test: Ability to disable DHCP, QA267.
Added sevaral test for security groups and dhcp.

Included all the remainding test but the multi-tenant ones.
Improved the functionality of the current scenario builder and
added several functions in relation to security groups.
fixed the comments of Daniel's code review
Merge pull request #10 from alvico/rebase_sg

Rebase sg