Update vOLT service to newer version

Change-Id: I2b4e70b751d218b918cd5edc3f9b2aee0adaaa8a
diff --git a/xos-profiles/att-workflow/requirements.yaml b/xos-profiles/att-workflow/requirements.yaml
index c7eb18d..6c6bade 100644
--- a/xos-profiles/att-workflow/requirements.yaml
+++ b/xos-profiles/att-workflow/requirements.yaml
@@ -24,7 +24,7 @@
   version: 2.1.5
   repository: file://../../xos-services/fabric
 - name: volt
-  version: 2.1.4
+  version: 2.1.5
   repository: file://../../xos-services/volt
 - name: fabric-crossconnect
   version: 1.1.2