Add instance_fault_create() to conductor

This moves the use of db.instance_fault_create() from the compute
utils to conductor.

Related to blueprint no-db-compute

Change-Id: If089ce1623374a259a2d63a99befc46fa3a130b6
Merge "Add instance_fault_create() to conductor"
Merge remote-tracking branch 'citrix/master' into build-temp