Description of problem:
When importing a virtual machine that has an invalid network defined in the OVF file the web interfaces gives a generic error of "Failed to import Vm host to ovirt".  The error message should be improved to indicate the the problem.  Users should also have the option of choosing a valid bridge.

Version-Release number of selected component (if applicable):
ovirt 3.1

How reproducible:
Create an OVF file with invalid network bridges and attempt an import

Steps to Reproduce:
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Actual results:
Error given "Failed to import Vm host to ovirt"

Expected results:
The error message should provide detail that the problem is with the bridge configuration in the OVF file.

Additional info: