tests: GET requests cannot have request body, use POST in rest.py
tests: GET requests cannot have request body, use POST in rest.py

Sending a request body with GET request is not valid in HTTP spec, and
not compatible with evhttpd.

dagurval/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,dagurval/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt,bitcoinxt/bitcoinxt