Description of problem:
Running engine-host-update.py with single host and running VM shows traceback. This traceback should be properly handled and only details should be displays.



Version-Release number of selected component (if applicable):
ovirt-engine-4.1.4.2-0.1.el7.noarch

How reproducible:
100%

Steps to Reproduce:
1. Have 1 host with running VM in engine
2. run `./engine-host-update.py --insecure --engine=localhost --username=admin@internal --password=mypass` --cluster=Default

Actual results:
Processing Host: moonmoon
Type: rhel
	Moving host to the maintenanceTraceback (most recent call last):
  File "./engine-host-update.py", line 684, in <module>
    processHost(api, host, skipInvalidHostNames)
  File "./engine-host-update.py", line 393, in processHost
    deactivateHost(api, name)
  File "./engine-host-update.py", line 213, in deactivateHost
    host.deactivate()
  File "/usr/lib/python2.7/site-packages/ovirtsdk/infrastructure/brokers.py", line 14293, in deactivate
    headers={"Correlation-Id":correlation_id}
  File "/usr/lib/python2.7/site-packages/ovirtsdk/infrastructure/proxy.py", line 122, in request
    persistent_auth=self.__persistent_auth
  File "/usr/lib/python2.7/site-packages/ovirtsdk/infrastructure/connectionspool.py", line 79, in do_request
    persistent_auth)
  File "/usr/lib/python2.7/site-packages/ovirtsdk/infrastructure/connectionspool.py", line 162, in __do_request
    raise errors.RequestError(response_code, response_reason, response_body)
ovirtsdk.infrastructure.errors.RequestError: 
status: 409
reason: Conflict
detail: The following Hosts have running VMs and cannot be switched to maintenance mode: moonmoon.Please ensure that the following Clusters have at least one Host in UP state: Default.


Expected results:
Error: The following Hosts have running VMs and cannot be switched to maintenance mode: moonmoon.Please ensure that the following Clusters have at least one Host in UP state: Default.