OS-531 Do not return None in infoblox_db

python returns None by default, remove unnecessary code from
infoblox_db.

Change-Id: Id72c6c8798a7d3e41a5c2e2ef5a65ad462bf0c9a
Merge pull request #11 from roman-verchikov/bp/infoblox-plugin-neutron

OS-531 Do not return None in infoblox_db
OS-425/OS-495, setup option 54 during network creation
Merge pull request #17 from Vegasq/OS-425

OS-425/OS-495, setup option 54 during network creation
Implement drivers for core plugins

Implements plugable way to get network information from L2 plugins.
Depending on core_plugin appropriate facade module gets loaded.
Currently contains drivers for ml2 and openvswitch.
Includes tests for new code.
OS-497 Fix EA names to match infoblox EA

EA were renamed from 'os_{ea_name}' to new names that
matches names declared in infoblox FS for VCO members.
Updated UT as well, and validated that new networks
created successfully on Juno.
Merge pull request #18 from bondar-pavel/rename-ea

OS-497 Fix EA names to match infoblox EA
OS-522 Rename init_l2() and Facade class

- Rename init_l2 to init_driver
- Rename Facade class to Driver class
- Fixed several comments
UT and manual tests passed fine with this patch
Merge pull request #12 from bondar-pavel/os-522

OS 522 Rework NetworkL2InfoProvider in plugable way
OS-479, DHCP service workflow fixes

    * dhcp_members was asigned but infoblox services wasnt restarted
    * dns server wasnt assigned in infoblox DHCP service