[lib-common] increase docker log speed. #748

Job	Run time
shellcheck	9s
Test script (gantry_cleanup_images_spec.sh)	35s
Test script (gantry_common_options_spec.sh)	46s
Test script (gantry_filters_spec.sh)	40s
Test script (gantry_jobs_spec.sh)	21s
Test script (gantry_login_docker_config_spec.sh)	21s
Test script (gantry_login_negative_spec.sh)	40s
Test script (gantry_login_spec.sh)	24s
Test script (gantry_manifest_spec.sh)	25s
Test script (gantry_notify_spec.sh)	31s
Test script (gantry_parallel_spec.sh)	23s
Test script (gantry_rollback_spec.sh)	26s
Test script (gantry_service_multiple_spec.sh)	20s
Test script (gantry_service_no_running_tasks_spec.sh)	37s
Test script (gantry_service_single_spec.sh)	20s
Test script (gantry_update_options_spec.sh)	24s
Build and push Docker image	0s
Test container	0s
	7m 22s

Provide feedback