CLOUDSTACK-7421
Unnecessary exception in MS logs while removing default NIC from VM. Following changes are made:
1. Changed the exception from CloudRuntimeException to InvalidParameterValueExecption.
2. Moved out validation logic to UserVMManagerImpl from VirtualMachineManagerImpl.
3. Handling InvalidParameterValueException from async API calls so that they are not logged as ERROR in MS logs.
CLOUDSTACK-7867: Delete network resulting in exception
Publish event was getting called from within a DB transaction which is not allowed.
CLOUDSTACK-7869: Add simulator support for findHostsForMigration API