Change log for DELL_OPENMANAGE

Date Changes
2022-07-27 Enhancement -
- Modified naming of host field from user_name to src_host in the grok.
- Mapped user to target.user.userid.
- Added null check for ip prior mapping to udm.
- Changed event_type from GENERIC_EVENT to STATUS_UPDATE where scr_host is not null.
- Added null check for date_time field.