Un-hardcode wsgi parameters

This patch adds abbility to configure the count of wsgi processes and
threads. The default parameters left intact to maintain backward
compatibility.

Closes-Bug: PROD-35385
Change-Id: I808e60d2db9b071a85adb840ce61592f49b62d91
diff --git a/README.rst b/README.rst
index 6b33e7a..f51f533 100644
--- a/README.rst
+++ b/README.rst
@@ -31,6 +31,7 @@
         enable_force_upload: true
         availability_zone_fallback: True
         image_conversion_dir: /var/tmp/cinder/conversion
+        wsgi_processes_count: 5
         concurrency:
           lock_path: '/var/lock/cinder'
         database: