Raise AgentBuildNotFound on updating/destroying deleted object
Raise AgentBuildNotFound on updating/destroying deleted object

Methods below should raise an exception when attempting to operate
with deleted AgentBuild objects:

 nova.db.sqlalchemy.api.agent_build_destroy()
 nova.db.sqlalchemy.api.agent_build_update()

Fixes: bug 1181967

Change-Id: If6df202afb7ea41634c35f7a52988e19677f4d65

n0ano/gantt,n0ano/gantt