Clarified location of driver config settings; removed ESX driver reference; minor text edits.

UPDATED part 3: Build failed! fixed program listing tags
UPDATED part 2: Build failed. Checked and modified tag formatting.
UPDATED: Removed tabs and applied correct use of <filename> tags.

* Clarified details of volume driver configuration settings for VMDK drivers in nova.conf and cinder.conf.

* Removed reference to ESX/ESXi server driver config because it has not been extensively tested.

* Changed occurrences of "data store" to "datastore" for consistency.

Change-Id: I2a45b131fa19749530f5fe93115518f8b9f4ea4e
backport: havana
Closes-Bug: #1260005
(cherry picked from commit abd25235ac3ea7c39b5899e536c7bf98321a3e1e)
Merge "Clarified location of driver config settings; removed ESX driver reference; minor text edits." into stable/havana