[gantry][tests] Handler warning better from docker command. Do not us… #852

Job	Run time
shellcheck	9s
Test scripts (gantry_cleanup_images_spec.sh)	57s
Test container	3m 4s
Test scripts (gantry_common_options_spec.sh)	1m 10s
Test scripts (gantry_filters_spec.sh)	53s
Test scripts (gantry_jobs_spec.sh)	46s
Test scripts (gantry_login_docker_config_spec.sh)	1m 54s
Test scripts (gantry_login_negative_spec.sh)	1m 56s
Test scripts (gantry_login_spec.sh)	1m 54s
Test scripts (gantry_manifest_spec.sh)	53s
Test scripts (gantry_notify_spec.sh)	2m 7s
Test scripts (gantry_parallel_spec.sh)	59s
Test scripts (gantry_rollback_spec.sh)	44s
Test scripts (gantry_service_multiple_spec.sh)	35s
Test scripts (gantry_service_no_running_tasks_spec.sh)	1m 11s
Test scripts (gantry_service_single_spec.sh)	48s
Test scripts (gantry_update_options_spec.sh)	59s
Build and push Docker image	0s
	20m 59s

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