mtest: handle should_fail in common code
mtest: handle should_fail in common code

This is common to all protocols, place the code in a single
place.

pexip/meson,jpakkane/meson,QuLogic/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,pexip/meson,jpakkane/meson,QuLogic/meson,QuLogic/meson,pexip/meson,QuLogic/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,pexip/meson,QuLogic/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,jpakkane/meson,jpakkane/meson