ConfigContext does not validate that JSON data is an object

[jeremystretch]

Environment

• Python version: 3.5.2
• NetBox version: 2.4.4

Steps to Reproduce

1. Create a new config context. Do not assign it to anything. (It will apply to all devices/VMs.)
2. Enter 1 as the data and save the config context.
3. Retrieve the rendered config context for a device.

Expected Behavior

Creating the config context with non-dictionary data should raise a validation error.

Observed Behavior

The config context was saved with the integer value. This causes a TypeError exception when attempting to retrieve the rendered context (either via the UI or API).