Fix module-instances command

Here's the code block in question:

        if instance_ids and len(instance_ids) > 1:
            raise exception.DatastoreOperationNotSupported(
                operation='module-instances', datastore='current')
            db_infos = DBInstance.query().filter_by(**query_opts)
        else:
            if instance_ids:
                query_opts['id'] = instance_ids[0]
            db_infos = DBInstance.find_all(**query_opts)

Fix proposed to branch: master
Review: https://review.openstack.org/403287

Reviewed: https://review.openstack.org/403287
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=a9a4ae4bba71db5e95070aad7009ebdffa7e20eb
Submitter: Jenkins
Branch: master

commit a9a4ae4bba71db5e95070aad7009ebdffa7e20eb
Author: Peter Stachowski <email address hidden>
Date: Thu Nov 3 13:56:41 2016 -0400

    Fix module-instances command

    Fixed the module-instances command to return a paginated
    list of instances. Also added a --count_only flag to the
    command to return a summary of the applied instances
    based on the MD5 of the module (this is most useful
    for live_update modules, to see which ones haven't been
    updated).

    Also cleaned up the code a bit, putting some methods
    into files where they made more sense (and would cause
    less potential collisions during import).

    Change-Id: I963e0f03875a1b93e2e1214bcb6580c507fa45fe
    Closes-Bug: #1554900

This issue was fixed in the openstack/trove 8.0.0.0b1 development milestone.