Fixes some typos spotted in a few Horizon files.

It fixes a few typos spotted in comments and debug/exception messages of these Horizon files:
 horizon/tables/base.py
 horizon/tables/formset.py
 horizon/tables/views.py
 horizon/utils/functions.py
 horizon/workflows/base.py

Change-Id: I7f3069df3f60a6a788f71870f9b49ffe23fdb5a6
Closes-Bug: #1268712
Merge "Fixes some typos spotted in a few Horizon files."