fix: claimed message require claim_id to delete

But bulk deletion can still delete both unclaimed and claimed
messages.  However, the major purpose to support bulk deletion
is to make it easy for a user to issue a DELETE on the Location
header returned from a POST; if a user intend to use claim, then
this URI does not help.

Change-Id: Ieed92fc0a07d2e873b729242fb2fb14536462780
Closes-Bug: #1215484
Merge "fix: claimed message require claim_id to delete"