Backport compute availabilityzones extension from the upstream

Change-Id: I2b824285af94669e1e57f61e4787b398e0db94d0
Related-PROD: PROD-34531
diff --git a/openstack/compute/v2/extensions/availabilityzones/testing/doc.go b/openstack/compute/v2/extensions/availabilityzones/testing/doc.go
new file mode 100644
index 0000000..a4408d7
--- /dev/null
+++ b/openstack/compute/v2/extensions/availabilityzones/testing/doc.go
@@ -0,0 +1,2 @@
+// availabilityzones unittests
+package testing