Plumb insecure flag to functests

The problem arises when running functests against pre-existing
clusters configured with self-signed certificates. As far as
security goes, doing that is rather useless, but it happens.
Such testing worked previously, but with the switch to Requests
in the client, we must plumb "insecure" flag. There's no other
way to do it in Requests, no environment variable, anything.

Change-Id: I94a61b60de8ee0529652c8c4a1ab9894c7cdb589
Merge "Plumb insecure flag to functests"