Remove SUPPORTED_AGENT_TYPES for l2pop

Remove SUPPORTED_AGENT_TYPES for l2pop

In a world where agents can be out of tree,
this check seems no longer necessary.

As part of networking-vsphere project which runs ovsvapp agent
on each ESXi host inside service VM, which talk to neutron-server
having l2pop enabled in a multi-hypervisor mode like KVM, ESXi.
The tunnels are not getting established between KVM compute node
and ESXi host. The l2pop mech_driver needs to embrace ovsvapp agent
to form the tunnels.

Hence, this patch-set addresses the issue by removing the
SUPPORTED_AGENT_TYPES for l2pop.

Closes-Bug: #1507684
Change-Id: I93ca5736e4aad41b851d2b7b082b4bb69d1632fb