Filebeat autodiscover hints fail to create inputs

[jsoriano]

Filebeat autodiscover hints don't create valid inputs on 7.2 branch, possibly related to #12162 and/or #12272.

For confirmed bugs, please report:

• Version: 7.2 branch
• Operating System: Linux
• Steps to Reproduce: Use filebeat with hints-based autodiscover

This error appears continuously in filebeat log:

2019-05-29T15:40:46.071Z	ERROR	[autodiscover]	cfgfile/list.go:96	Error creating runner from config: each input must have at least one path defined

Tested configuration:

    filebeat.autodiscover:
      providers:
        - type: kubernetes
          hints.enabled: true

There is a workaround with the new possibility of adding a different default config (#12272), this works:

    filebeat.autodiscover:
      providers:
        - type: kubernetes
          hints.enabled: true
          hints.default_config:
            type: container
            paths:
              - /var/log/containers/*${data.container.id}.log