Add whitespace surpression to redisdb.yaml.erb to ensure a valid yaml

[Aramack]

Add white space suppression to redisdb.yaml.erb to ensure a valid yaml file is output.

Currently multiple keys or tags will break the indentation. EG:

class { 'datadog_agent::integrations::redis' :
  host => 'localhost',
  keys => ['foo','bar'],
  tags => ['foo:bar','spam:egg'],
}

Will output invalid yaml:

### MANAGED BY PUPPET

init_config:

instances:
  - host: localhost
    port: 6379
    warn_on_missing_keys: true
    command_stats: false
    keys:
      - foo
        - bar
      tags:
      - foo:bar
        - spam:egg

With this change applied, the output will be valid yaml:

### MANAGED BY PUPPET

init_config:

instances:
  - host: localhost
    port: 6379
    warn_on_missing_keys: true
    command_stats: false
    keys:
      - foo
      - bar
    tags:
      - foo:bar
      - spam:egg

[albertvaka]

Hi Aramack! I just tested your fix and it works like a charm!

Thanks for a lot for spotting this and taking the time to fix it 😄

Merging!