placement: Install OSC plugin, poll for readiness
placement: Install OSC plugin, poll for readiness

In Bionic/Ussuri UCA, the placement OSC plugin was absent
and not packaged. Now that it is present in Focal, install
it and use it to poll for placement API readiness.

Signed-off-by: Tyler Stachecki <ac19b26ca570cbd1d833044669caf79cb1d18c48@bloomberg.net>

bloomberg/chef-bcpc,bloomberg/chef-bcpc,bloomberg/chef-bcpc,bloomberg/chef-bcpc