[Params] Define HostIdSet.
[DBTablesHost] Implement getVirtualMachines().
[DBTablesHost] Use tableProfileHostHostgroup for checking host access.
[DBTablesTest] Use the new host tables.

I will squash this commit in the clean up later.
[DBTablesTest] Add test data.
[testDBTablesHost] Clean up a test for getVirtualMachines().
Merge pull request #777 from project-hatohol/host-management-4c

Host management 4c