API: Move "x-nullable: true" from type PortBinding to type PortMap
Currently the API spec would allow `"443/tcp": [null]`, but what should
be allowed is `"443/tcp": null`
@@ -1154,6 +1154,7 @@ definitions:
type: "object"
additionalProperties:
type: "array"
+ x-nullable: true
items:
$ref: "#/definitions/PortBinding"
example:
@@ -1178,7 +1179,6 @@ definitions:
PortBinding represents a binding between a host IP address and a host
port.
type: "object"
- x-nullable: true
properties:
HostIp:
description: "Host IP address that the container's port is mapped to."
