Fix misspellings in devstack

Fix misspellings detected by:
 * pip install misspellings
 * git ls-files | grep -v locale | misspellings -f -

Change-Id: I19726438d15cd27b813504aac530e7e53c4def12
Closes-Bug: #1257295
Merge "Fix misspellings in devstack"
Merge branch 'master' of github.com:openstack-dev/devstack