Correct exception for flavor extra spec create/update

When create/update flavor extra spec failed for v2 api, it will not
raise MetadataLimitExceeded for but two exceptions as following:
1) FlavorExtraSpecUpdateCreateFailed
2) FlavorNotFound

When create/update flavor extra spec failed for v3 api, it will not
raise DBDuplicateEntry but raise FlavorExtraSpecUpdateCreateFailed.

This patch updates the exception handling logic for create/update
flavor extra spec.

Change-Id: If3310a1cb44952e8fe2efe0b3358783f729bc190
Merge "Correct exception for flavor extra spec create/update"