correcting for proper use of the word 'an'.

Change-Id: Ib6180284d806a00c520df378e651fba947e2397a
PXE driver should not accept empty kernel UUID.

Baremetal PXE driver was aborting only if the kernel and ramdisk
specified in image metadata were None, but not if they were another
non-true value, such as "". Now, exception is raised if they are any
non-true value.

Fix bug 1100589.

Change-Id: I9783a14cc242e1b9db04d797c61d54b06d52c680
Remove restoring soft deleted entries part 1

There is no need to reuse deleted entries, because they will be archived after
db-archiving implementation. And restoring soft deleted entries produce some
problem with db-unique-keys implementation. So the best way is to remove it.

instance_type_access_add() method
Remove restoring soft deleted instance_type_access entries

instance_type_extra_specs_update_or_create() method
Remove restoring soft deleted instance_type_extra_specs entries
Add missing transaction

aggregate_host_add() method
Remove restoring soft deleted aggreagate_hosts entries
Add missing transaction

blueprint db-session-cleanup

Change-Id: Ida7db95233c40faacac55105650f52d42ad360c2
Merge "PXE driver should not accept empty kernel UUID."
Merge "correcting for proper use of the word 'an'."
Merge "Remove restoring soft deleted entries part 1"
Merge remote-tracking branch 'citrix/master' into build-temp