[ML] Saved search where kibana has index pattern with comma separated values create invalid datafeed

[jguay]

Kibana version:
7.6.2
Elasticsearch version:
7.6.2
Describe the bug:
When saved search use index-pattern with multiple entries like indexa,indexb, datafeed definition is invalid and result in no match
Steps to reproduce:

1. Create index pattern in kibana with comma separated values ".monitoring-es*,.monitoring-e*"
2. Go to Discover and save the search
3. Create ML job based on saved search

Expected behavior:
Should see data coming though
Provide logs and/or server output (if relevant):
GET _ml/datafeeds returns :

{
  "count" : 1,
  "datafeeds" : [
    {
      "datafeed_id" : "datafeed-test2wildcardedpatterns",
      "job_id" : "test2wildcardedpatterns",
      "query_delay" : "88230ms",
      "indices" : [
        ".monitoring-es*,.monitoring-e*"
      ],
      "query" : {
        "bool" : {
          "must" : [
            {
              "match_all" : { }
            }
          ],
          "filter" : [ ],
          "must_not" : [ ]
        }
      },
      "aggregations" : {
        "buckets" : {
          "date_histogram" : {
            "field" : "timestamp",
            "fixed_interval" : "900000ms"
          },
          "aggregations" : {
            "timestamp" : {
              "max" : {
                "field" : "timestamp"
              }
            }
          }
        }
      },
      "scroll_size" : 1000,
      "chunking_config" : {
        "mode" : "manual",
        "time_span" : "900000000ms"
      },
      "delayed_data_check_config" : {
        "enabled" : true
      }
    }
  ]
}

Data shows correctly after the datafeed is modified from :

"indices" : [
        ".monitoring-es*,.monitoring-e*"
      ]

to 2 valid separate entries

"indices" : [
        ".monitoring-es*",".monitoring-e*"
      ]

[jgowdyelastic]

This bug is also present in non-saved search jobs.

1. Create index pattern in kibana with comma separated values ".monitoring-es*,.monitoring-e*"
2. Create a job using this index pattern.