test: Quiesce Chromium logorhea
test: Quiesce Chromium logorhea

Recent chromium versions (seen with 85.0.4183.121) have become
ridiculously chatty, spewing thousands of messages like

    ERROR:paint_controller.cc(646)] PaintController::FinishCycle() completed
    VERBOSE2:thread_state.cc(429)] [state:0x560d0d8fefc0] ScheduleGCIfNeeded

Explicitly set verbosity 0. This was, and is supposed to be, the
default, but apparently not any more.

Closes #14683
deryni/cockpit,martinpitt/cockpit,deryni/cockpit,garrett/cockpit,mvollmer/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,garrett/cockpit,garrett/cockpit,mvollmer/cockpit,martinpitt/cockpit,deryni/cockpit,mvollmer/cockpit,cockpit-project/cockpit