Adds instance lock check for live migrate

Whilst migrate has an instance locked check, live migrate didn't. This patch
adds a check to see if the instance is locked in the compute api live migrate.

Adds a testcase for V3 and generic instance lock checking for the V2 API since
none existed yet.

Closes-bug: 1257187

Change-Id: I442abb74fe2a4d5d46b597b0ea24d249d2d03b45
Downgrade some exception LOG messages in the ec2 API

Downgrades some LOG.exception messages to more appropriate error
or debug level instead. Tracebacks should only be produced where
they are really necessary. In two of the cases the error path is entirely
expected as a result from user error and should therefore only be
logged at debug level.

Change-Id: Ib8321836c622a30c37c97fa971cb9fcf406bd2f1
Add API schema for v2.1/v3 quota_sets API

By defining the API schema, it is possible to separate the validation
code from the API method. The API method can be more simple.
In addition, a response of API validation error can be consistent for
the whole Nova API.

Partially implements blueprint v3-api-schema

Change-Id: I90c7a82a017cd67328f390c8a9bd0774d61139bd
Merge "Downgrade some exception LOG messages in the ec2 API"
Merge "Add API schema for v2.1/v3 quota_sets API"
Merge "Adds instance lock check for live migrate"