Skip 'shocco' code when running tox

when running tox in a devstack directory where you have previously run tox
-edocs the bashate testenv will fail as the shocco code doesn't match the
devstack style.

eg:
---
E003: Indent not multiple of 4: '           2>/dev/null ||'
 - /home/stack/projects/openstack/openstack-dev/devstack/shocco/shocco.sh : L352
<snip>
27 bashate error(s) found
---

Take the easy path and avoid running bashate in the shocco dir.

Change-Id: I5b0155332ec994afaffc5c5961902281864cff61

tox.ini

@@ -13,6 +13,7 @@ whitelist_externals = bash
 commands = bash -c "find {toxinidir}             \
          -not \( -type d -name .?\* -prune \)    \ # prune all 'dot' dirs
          -not \( -type d -name doc -prune \)     \ # skip documentation
+         -not \( -type d -name shocco -prune \)  \ # skip shocco
          -type f                                 \ # only files
          -not -name \*~                          \ # skip editors, readme, etc
          -not -name \*.md                        \