HPCC-10515 Use POST to send ZAP Report request

The existing code uses HTTP Get method to send ZAP Report request.
When a ZAP Report request contains a large size parameter, the
parameter will be trancated and a Bad request error shows. In this
fix, the HTTP POST method is used to send ZAP Report request.

Signed-off-by: Kevin Wang <kevin.wang@lexisnexis.com>