A new configuration variable nsx_extension_drivers
has been added. This is in the DEFAULT section. This enable us
to code support to add via configurations extensions, for
example dns_integration.
Co-authored-by: Shih-Hao Li <shihli@vmware.com>
Change-Id: Iea4715522d9c7cf327b7f1a751b78f14d5e06e75