Apply service name conventions for Compute

There are several instances of "Compute Service" and "compute service"
in the upstream documentation. As was recently clarified in the docs
mailing list, these should be "Compute service/s". This patch corrects
all untagged instances inside normal <para> blocks.

Change-Id: Idcd7aafa0ce463e70635cb1c883a2476c1d97b5e
Partial-Bug: #1217503
Merge "Apply service name conventions for Compute"