Keystone uwsgi performance tuning

I ran some tests locally that showed that when using the uwsgi
deploy the keystone server wasn't using all the processes
available. When I switched from "threads" to "processes" the
concurrent performance improved considerably. So I'm proposing
that devstack switch to processes to improve performance.

Change-Id: I8cfe9272e098e636441b7cfb51bff08d62c3336e
diff --git a/lib/keystone b/lib/keystone
index c94bcd3..26fa1d4 100644
--- a/lib/keystone
+++ b/lib/keystone
@@ -318,10 +318,10 @@
         fi
 
         iniset "$KEYSTONE_PUBLIC_UWSGI_FILE" uwsgi wsgi-file "$KEYSTONE_BIN_DIR/keystone-wsgi-public"
-        iniset "$KEYSTONE_PUBLIC_UWSGI_FILE" uwsgi threads $(nproc)
+        iniset "$KEYSTONE_PUBLIC_UWSGI_FILE" uwsgi processes $(nproc)
 
         iniset "$KEYSTONE_ADMIN_UWSGI_FILE" uwsgi wsgi-file "$KEYSTONE_BIN_DIR/keystone-wsgi-admin"
-        iniset "$KEYSTONE_ADMIN_UWSGI_FILE" uwsgi threads $API_WORKERS
+        iniset "$KEYSTONE_ADMIN_UWSGI_FILE" uwsgi processes $API_WORKERS
 
         # Common settings
         for file in "$KEYSTONE_PUBLIC_UWSGI_FILE" "$KEYSTONE_ADMIN_UWSGI_FILE"; do