20183: Clean up sql queries.

20183: Clean up sql queries.

Remove "container_requests.uuid IS NOT NULL" (this is a tautology in
an inner join)

Use same "state=Committed" condition in Rails and controller
query. This is already implied by the "containers.state in (Queued,
Locked, Running)" condition since only a Committed request should
reference such a container. However, if the distinction ever comes
up (race?  manual database update?) we would want to skip the
non-Committed requests, so this serves as cheap insurance.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>