Fix TEMPEST_AUTH_VERSION comparision condition for identity v2

TEMPEST_AUTH_VERSION should be 'v3' or 'v2' not 'v2.0'.
To disable the identity v2 admin tests TEMPEST_AUTH_VERSION is
being compared with 'v2.0' which is incorrect.

Change-Id: I5f7e3bcf733edbbee06016bcad4845dda552815e
diff --git a/lib/tempest b/lib/tempest
index 60f571c..f83476d 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -279,8 +279,8 @@
         iniset $TEMPEST_CONFIG identity-feature-enabled api_v2 False
     fi
     iniset $TEMPEST_CONFIG identity auth_version ${TEMPEST_AUTH_VERSION:-v3}
-    if [[ "$TEMPEST_AUTH_VERSION" != "v2.0" ]]; then
-        # we're going to disable v2 admin unless we're using v2.0 by default.
+    if [[ "$TEMPEST_AUTH_VERSION" != "v2" ]]; then
+        # we're going to disable v2 admin unless we're using v2 by default.
         iniset $TEMPEST_CONFIG identity-feature-enabled api_v2_admin False
     fi