HTTP_Adapter: split into f_http_tx_request() / f_http_rx_response()

There are some use cases in which we don't want a blocking wait for the
full HTTP request to complete.  Let's split it up in two parts, and
make the existing f_http_transact() a wrapper around them.

Also, enable the generation of the Connect_result primitive to detect
connection failures.

Change-Id: I5c7575c0b58c3606d25d8f8cfccd47cfb7a8c400
2 files changed