ORCA version is: orca-iaas-5.4.0_0_g0ece627-201801251206.

In /root/modify_failures_02_19_2018 (on tamu-hn), we have evidence of handler code not properly failing and returning errors upstream. This issue is a follow-on to: #208

At line 844 of: handlers/ec2/resources/handlers/ec2/handler.xml

We call the python script "neuca-quantum-add-iface" - but we do not properly handle errors that may have occurred as a result of its execution (so that they could be propagated upstream to ORCA).

As a result, modify attempts that add interfaces to VMs appear to succeed - despite having actually failed to properly perform the actions required for the modify request.