Bump working version to 4

With the tempest-3 tag being published to signify the end of xml
testing in tempest we need to bump the working version to tempest-4
to indicate that the next tag will be 4.

Change-Id: I1fd12cb3e20692c60daa4eb19c6d876b00318d56
diff --git a/setup.cfg b/setup.cfg
index 90ea944..1e7cc2b 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = tempest
-version = 3
+version = 4
 summary = OpenStack Integration Testing
 description-file =
     README.rst