we only use one passed and one piped requests, so our servers should
only ever see two requests.

Motivated by a failure on fedora armv7hl, which I do not understand:

**   c1    === txreq -url /1 -hdr "pipe: true"
**** c1    txreq|GET /1 HTTP/1.1\r
**** c1    txreq|pipe: true\r
**** c1    txreq|Host: 127.0.0.1\r
**** c1    txreq|\r
**   c1    === rxresp
**** dT    3.832
**** c1    rxhdrlen = 0
---- c1    HTTP header is incomplete
**** dT    3.833