[gantry][tests] Handler warning better from docker command. Do not us… #865

Job	Run time
shellcheck	10s
Test scripts (gantry_cleanup_images_spec.sh)	1m 5s
Test container	3m 14s
Test scripts (gantry_common_options_spec.sh)	1m 7s
Test scripts (gantry_filters_spec.sh)	55s
Test scripts (gantry_jobs_spec.sh)	42s
Test scripts (gantry_login_docker_config_spec.sh)	1m 0s
Test scripts (gantry_login_negative_spec.sh)	1m 9s
Test scripts (gantry_login_spec.sh)	1m 4s
Test scripts (gantry_manifest_spec.sh)	1m 2s
Test scripts (gantry_notify_spec.sh)	1m 14s
Test scripts (gantry_parallel_spec.sh)	1m 0s
Test scripts (gantry_rollback_spec.sh)	54s
Test scripts (gantry_service_multiple_spec.sh)	39s
Test scripts (gantry_service_no_running_tasks_spec.sh)	51s
Test scripts (gantry_service_single_spec.sh)	48s
Test scripts (gantry_update_options_spec.sh)	55s
Build and push Docker image	0s
	17m 49s

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