Find installer exceptions

Rearrange the imports in ovirt.node.config.migrate so we only
try to clear out one augeas object when we exit.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1085835

Change-Id: Ida10fd5ae68d2b8eececd58d154adf9d3042ff28
Signed-off-by: Ryan Barry <rbarry@redhat.com>