Don't emit Length records for piped requests
Don't emit Length records for piped requests

We don't have a file descriptor for piped requests, so just don't emit
a Length record.

Fixes: #923

wikimedia/operations-debs-varnish,feld/Varnish-Cache,ssm/pkg-varnish,ajasty-cavium/Varnish-Cache,mrhmouse/Varnish-Cache,zhoualbeart/Varnish-Cache,ssm/pkg-varnish,gauthier-delacroix/Varnish-Cache,zhoualbeart/Varnish-Cache,ajasty-cavium/Varnish-Cache,zhoualbeart/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,ambernetas/varnish-cache,ajasty-cavium/Varnish-Cache,zhoualbeart/Varnish-Cache,drwilco/varnish-cache-drwilco,wikimedia/operations-debs-varnish,gauthier-delacroix/Varnish-Cache,zhoualbeart/Varnish-Cache,ambernetas/varnish-cache,ambernetas/varnish-cache,chrismoulton/Varnish-Cache,franciscovg/Varnish-Cache,gauthier-delacroix/Varnish-Cache,franciscovg/Varnish-Cache,franciscovg/Varnish-Cache,varnish/Varnish-Cache,1HLtd/Varnish-Cache,ssm/pkg-varnish,ajasty-cavium/Varnish-Cache,chrismoulton/Varnish-Cache,drwilco/varnish-cache-drwilco,wikimedia/operations-debs-varnish,franciscovg/Varnish-Cache,1HLtd/Varnish-Cache,chrismoulton/Varnish-Cache,feld/Varnish-Cache,wikimedia/operations-debs-varnish,mrhmouse/Varnish-Cache,alarky/varnish-cache-doc-ja,1HLtd/Varnish-Cache,chrismoulton/Varnish-Cache,varnish/Varnish-Cache,1HLtd/Varnish-Cache,franciscovg/Varnish-Cache,feld/Varnish-Cache,ssm/pkg-varnish,gquintard/Varnish-Cache,gauthier-delacroix/Varnish-Cache,varnish/Varnish-Cache,alarky/varnish-cache-doc-ja,alarky/varnish-cache-doc-ja,ajasty-cavium/Varnish-Cache,alarky/varnish-cache-doc-ja,feld/Varnish-Cache,gquintard/Varnish-Cache,mrhmouse/Varnish-Cache,ssm/pkg-varnish,gquintard/Varnish-Cache,drwilco/varnish-cache-drwilco,wikimedia/operations-debs-varnish,varnish/Varnish-Cache,chrismoulton/Varnish-Cache,alarky/varnish-cache-doc-ja,mrhmouse/Varnish-Cache,varnish/Varnish-Cache,gauthier-delacroix/Varnish-Cache,mrhmouse/Varnish-Cache