Allow users the ability to update the instance name

Currently the users do not have the ability to rename an
instance. The current PUT call, does not allow the user
to modify individual attributes of the instance.
Hence this review introduces a new PATCH call for updating
instance name and/or configurations.
The long term plan is to deprecate PUT in favor of PATCH.

Implements: blueprint update-instance-name

Change-Id: I25c3b0906191afdc587f5ddd5777b3185dc080d4