gce_gahp wasn't reporting errors for GCE_INSTANCE_LIST command. #6712
gce_gahp wasn't reporting errors for GCE_INSTANCE_LIST command. #6712

Add missing return statement. Otherwise, error result is overwritten by
bogus success result indicating all instances have exited.

htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor