charm: Add cover tox job

Change-Id: Id32ab56cb0d11d253db92b7978df118814480861
diff --git a/zuul.d/charm-cinder-storpool-iscsi.yaml b/zuul.d/charm-cinder-storpool-iscsi.yaml
index aa5031e..7207178 100644
--- a/zuul.d/charm-cinder-storpool-iscsi.yaml
+++ b/zuul.d/charm-cinder-storpool-iscsi.yaml
@@ -112,6 +112,12 @@
     vars:
       tox_env: lint
 
+- job:
+    name: charm-tox-cover
+    parent: charm-tox
+    vars:
+      tox_env: cover
+
 - project:
     name: charm-cinder-storpool-iscsi
     check:
@@ -122,6 +128,8 @@
             branches: master
         - charm-tox-lint:
             branches: master
+        - charm-tox-cover:
+            branches: master
         - zaza-functional-focal-ussuri:
             branches: master
     experimental: