Fix logic for aggregate_metadata_get_by_host_with_key test case

After deleting a3 metadata, it is the host that once has such metadata
should be tested.

Change-Id: I79c40aa977911cd327d478ad8d9f147e19325017
Revert "Address the comments of the merged image handler patch"

This file was added in a55bbbfa1957d02b3006a51afcf4984a1f8ff886 and
later fixed up in 9e8513e6fe4bf8a8759ad0c1d71594f952d920ad. Only the
first commit was reverted in 0ba9cca788309bd8763a0d277a907769604cd9f4,
this commit finishes the job and reverts the fix-up commit so that the
orphan imagehandler code doesn't linger and doesn't get in the way of
future changes.

This reverts commit 9e8513e6fe4bf8a8759ad0c1d71594f952d920ad.

Change-Id: I3cf8000a3e984c57441a226d3139acbf3e346825
Remove and block DB access in dhcpbridge

This fixes an issue of direct DB access from happening in dhcpbridge
by using an object method instead. For this to work and to prohibit
future DB access from happening, the objects indirection API is set
and DB access is blocked in a similar way to how it is done in
nova-compute and nova-network.

Change-Id: I5e3152aad13343a6a1ecd9b5b511429159c9d4c2
Closes-Bug: #1316074
Merge "Remove and block DB access in dhcpbridge"
Merge "Revert "Address the comments of the merged image handler patch""
Merge "Fix logic for aggregate_metadata_get_by_host_with_key test case"