The legacy v2 API allowed None for the boot_index [1]. It
allowed this implicitly because the API code would convert
the block_device_mapping_v2 dict from the request into a
BlockDeviceMapping object, which has a boot_index field that
is nullable (allows None).
The API reference documentation [2] also says:
"To disable a device from booting, set the boot index
to a negative value or use the default boot index value,
which is None."
It appears that with the move to v2.1 and request schema
validation, the boot_index schema was erroneously set to
not allow None for a value, which is not backward compatible
with the v2 API behavior.
This change fixes the schema to allow boot_index=None again
and adds a test to show it working.
This should not require a microversion bump since it's fixing
a regression in the v2.1 API which worked in the v2 API and
is already handled throughout Nova's block device code.
Closes-Bug: #1662699
[1] https://github.com/openstack/nova/blob/13.0.0/nova/compute/api.py#L1268
[2] http://developer.openstack.org/api-ref/compute/#create-server
Change-Id: Ice78a0982bcce491f0c9690903ed2c6b6aaab1be