Rename congress_policy_client to congress_client

congress_policy_client is a really long string and thus causes
a lot of line wrapping. This patch removes policy from its name to
help with that in addition having policy in the client name is
doesn't really improve anything.

Change-Id: Ia69ef00e475698751d8fd9a4bda4ff58199e12f5
Merge "Rename congress_policy_client to congress_client"