Use threading.ThreadError instead of reraising IOError

The threading API specifies that ThreadError should
be used as the common exception raised from threading
and locking apis so instead of reraising an IOError
reraise a new ThreadError one instead.

Change-Id: Ic06dd211a8a5da074623ac449d27e963dd5ba754
Small edits on help strings

These were initially noted during import into the manuals at
https://review.openstack.org/67502

Fixes include rework of text, missing or extra spaces, wrong
capitalization and no sentence style capitalization.

Change-Id: I56a47de73e0e494a6f770e29dae8065b398ef5af
Co-Authored-By: Diane Fleming <diane.fleming@rackspace.com>
Merge "Use threading.ThreadError instead of reraising IOError"
Merge "Small edits on help strings"