chunk-test: add a check that wrote-body-data gives the right data
chunk-test: add a check that wrote-body-data gives the right data

(This was already working, but not tested, on master, but it was
broken on a work branch.)

Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,fanc999/libsoup,jwendell/libsoup,Distrotech/libsoup,jwendell/libsoup,fanc999/libsoup,Distrotech/libsoup,jwendell/libsoup,Distrotech/libsoup,fanc999/libsoup,jwendell/libsoup,fanc999/libsoup,fanc999/libsoup