Bypass queries which cause a contradiction

This addresses the cause of the log lines like:

SAWarning: The IN-predicate on "instance_system_metadata.instance_uuid"
was invoked with an empty sequence. This results in a contradiction,
which nonetheless can be expensive to evaluate. Consider alternative
strategies for improved performance.

for instance_metadata, instance_system_metadata, and instance_faults.

It especially helps the case of a call to /servers/detail when there are
no servers to list because each of those tables is scanned despite a
guarantee that there will be now rows.

Bug 1204916

Change-Id: I62e65c4409d3e3ab8373eb66450414565c222547
Merge "Bypass queries which cause a contradiction"