Add GANTRY_NOTIFICATION_CONDITION #67

Job	Run time
shellcheck	6s
Run tests (gantry_cleanup_images_spec.sh)	1m 55s
Run tests (gantry_common_options_spec.sh)	1m 29s
Run tests (gantry_filters_spec.sh)	1m 8s
Run tests (gantry_login_spec.sh)	2m 7s
Run tests (gantry_manifest_spec.sh)	1m 47s
Run tests (gantry_notify_spec.sh)	1m 46s
Run tests (gantry_parallel_spec.sh)	1m 57s
Run tests (gantry_rollback_spec.sh)	58s
Run tests (gantry_service_multiple_spec.sh)	1m 51s
Run tests (gantry_service_no_running_tasks_spec.sh)	1m 29s
Run tests (gantry_service_single_spec.sh)	1m 32s
Run tests (gantry_update_options_spec.sh)	1m 52s
	19m 57s

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