Previously NSXv3 LBaaS driver only supports creating lb pool with
listener as LBaaS v2.0 spec. Since octavia api also allows
creating lb pool either with listener or loadbalancer, refactor
driver to support both cases.
Also in this patch, moved lb binding deletion from member_mgr to
loadbalancer_mgr. One loadbalancer can have multiple pools, the
lb binding cannot be deleted if there is other pools on the lb.
Fixing the unit tests as well.
Change-Id: Ia138eda4957f335c45ab4a9589a389baf0f7d676
dcd5bdb0f3