Remove [placement]/os_region_name usage

The [placement]/os_region_name config option is deprecated
and no longer required to be set (the default is fine for
devstack) with the dependent nova change.

Depends-On: I973180d6a384b32838ab61d4e6aaf73c255fd116

Change-Id: I6379acf179ed511f1cdadbd7fb09e2454182a5d3
diff --git a/lib/placement b/lib/placement
index 1d68f8a..2343ac9 100644
--- a/lib/placement
+++ b/lib/placement
@@ -112,7 +112,6 @@
     iniset $conf placement user_domain_name "$SERVICE_DOMAIN_NAME"
     iniset $conf placement project_name "$SERVICE_TENANT_NAME"
     iniset $conf placement project_domain_name "$SERVICE_DOMAIN_NAME"
-    iniset $conf placement os_region_name "$REGION_NAME"
     # TODO(cdent): auth_strategy, which is common to see in these
     # blocks is not currently used here. For the time being the
     # placement api uses the auth_strategy configuration setting