http-fetch: invoke trace2_cmd_name()

http-fetch: invoke trace2_cmd_name()

ee4512ed48 ("trace2: create new combined trace facility", 2019-02-
22) introduced trace2_cmd_name() and taught both the Git built-ins and
some non-built-ins to use it. However, http-fetch was not one of them
(perhaps due to its low usage at the time).

Teach http-fetch to invoke this function. After this patch, this
function will be invoked right after argument parsing, just like in
remote-curl.c.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>