Update toci_gate_test.sh to use the broker.

toci_gate_test now enters the broker and chains into toci_devtest.sh
via test-envclient. Under the hood this is doing:

$ testenv-client -b <geardserver>:4730 -- ./toci_devtest.sh

This depends on both a gearman broker and at least one registered
test env being deployed.

toci_devtest includes the code to apply the broker supplied SSH key to
the system and then attempts to run the first few stages of devtest,
preserving the test environment definintion from the broker.

The astute of eye may observe that we haven't solved how to pass the gear
server host into the test environment yet... that may require an
openstack-infra/config patch.

Change-Id: I53ce4ca687283a924ea055267ea90f20d6632651
Co-Authored-By: Robert Collins <rbtcollins@hp.com>
Merge "Update toci_gate_test.sh to use the broker."