test-utils: set GSETTINGS_BACKEND=memory
test-utils: set GSETTINGS_BACKEND=memory

To ensure we don't get unwanted proxy settings, and so we don't get
warnings if the memory backend is the only one available.

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