CLOUDSTACK-3902: createVpcOffering - throw an excpetion when sourceNat service is not passed in
[GSOC] Mesos integration mid-term report

Signed-off-by: Sebastien Goasguen <runseb@gmail.com>
Summary: Fix null pointer and op_networks blocker to account cleanup

Detail: Accounts can fail in cleanup/gc process due to inconsistent op_networks
table and null pointer in looking up account for event publishing.

BUG-ID: CLOUDSTACK-3957
Signed-off-by: Marcus Sorensen <marcus@betterservers.com> 1375204815 -0600