Don't rewrite the NotFound error message

When user updates an image with a nonexisted location, it's
expected to run into location not found exception. However,
because the error message is rewritten in v2 image update,
so user will get below wrong message:
Failed to find image <image-id> to update

This fix will remove the rewritten message, given the NotFound
message has been set at: glance/db/sqlalchemy/api.py#L159

Closes-Bug: #1265448

Change-Id: I4e5fbbe40ce0fd13e828a40a424d4fcdc66a236b
Don't override transport_url with old configs

The backwards compatibility support turned out being a forward
compatibility blocker. This patch attempts to first load the notifier
transport using the transport_url and then, if the transport_url was not
configured, it loads the transport by using the old strategy config
params.

Closes-bug: #1263945

Change-Id: I4c80c64e2d1afaf518886b51a50300a576ee6317
Merge "Don't override transport_url with old configs"
Merge "Don't rewrite the NotFound error message"