[Filebeat] Fields for module fileset are not parsed when Grok pattern define also type of the field

[radoondas]

Hi!
When generating the base field.yml file from pipeline definition in module's fileset, fields with type definition are ignored or not parsed. They do not appear in fields.yml file. All others are just fine.

Example definition: %{NUMBER:elasticsearch.slowlog.total_hits:int}
Example command for file generation: make create-fields MODULE=elasticsearch FILESET=slowlog

Thanks