Reset migrating task state for more Exceptions

There are a number of exceptions that can occur during pre
live-migration checks, and they should reset the task state to None when
they occur since they prevent the migration from beginning.  This adds
two more exceptions to the list of exceptions that just need to reset
the task state rather than set the instance to error.

Bug 1100462

Change-Id: I95e09f49908fbc3a79f5d2eb490d5a0b3296a6ed
Merge "Reset migrating task state for more Exceptions"