tests: use two roundtrips for global events
tests: use two roundtrips for global events

first is for getting and binding to globals and the other one is for
getting wl_shm.formats that are emitted after binding
to wl_shm

Signed-off-by: Marek Chalupa <a05df156a69ad59faa9af9b666ef78009594c145@gmail.com>
Reviewed-by: Daniel Stone <62e7e355d5d8400fa8384448796af0bf6be4ffae@collabora.com>
Reviewed-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

krezovic/weston,giucam/weston,sir-murray/weston,kwm81/weston,udoprog/weston,krezovic/weston,kwm81/weston,giucam/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,eyolfson/weston,mchalupa/weston,Fantu/compositor-spice,xorgy/weston,Gnurou/weston,xorgy/weston,jonnylamb/weston,eyolfson/weston,Gnurou/weston,mchalupa/weston,udoprog/weston,Fantu/compositor-spice,jonnylamb/weston,Tarnyko/weston-xdg_surface_present,sir-murray/weston