cube: roundtrip to ensure all globals are processed

[vyivel]

wl_display_dispatch() may not process all events.

[ci-tester-lunarg]

Author vyivel not on autobuild list. Waiting for curator authorization before starting CI build.

[ci-tester-lunarg]

Author vyivel not on autobuild list. Waiting for curator authorization before starting CI build.

[CLAassistant]

All committers have signed the CLA.

[charles-lunarg]

Apologies for the delay in merging, I wanted to let CI finish and forgot to hit merge...