HPCC-12339 Change user's filter for logical file name to lower case

In WsDFU.DFUQuery, a user may type in a logical file name or a
prefix as a filter. Upper case value inside the filter should be
changed to lower case before using as the filter of the DFUQuery.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
Merge pull request #6492 from wangkx/h12339

HPCC-12339 Change user's filter for logical file name to lower case

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>