Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1498447

Description of problem:
Sometimes, when creating a new RHEV host through a dialog, after clicking submit and long waiting (probably related to some timeout), the error message is shown:

"Oops, we're sorry but something went wrong undefined method `persisted?' for nil:NilClass"

With the attached traceback.

Version-Release number of selected component (if applicable):
Reproduced on Sat6.3 snap 18.

How reproducible:
Sometimes, probably after timeout

Steps to Reproduce:
1. Hosts -> Create Host
2. Fill in the form, using RHEV computing resource as "Deploy on"
3. Submit

Actual results:
Error, traceback, operation fails

Expected results:
New host created