Bump MCAPI to 0.26.2

Change-Id: Id54ff0c35d8a065a733cd10b51ac580d01261758
diff --git a/images/magnum/Dockerfile b/images/magnum/Dockerfile
index 833e2c3..b2a7f4c 100644
--- a/images/magnum/Dockerfile
+++ b/images/magnum/Dockerfile
@@ -21,7 +21,7 @@
 pip3 install \
     --constraint /upper-constraints.txt \
         /src/magnum \
-        magnum-cluster-api==0.26.0
+        magnum-cluster-api==0.26.2
 EOF
 
 FROM openstack-python-runtime