The tgt task should install the packages it needs.
We'd like to stop installing scsi-target-utils and iscsi-initiator-utils on rhel 6.x because it has a requirement on librbd1 and librados. This makes our ansible playbooks not idempotent because whenever we install scsi-target-utils it installs librd1 and librados. We also make sure that librd1 and librados are absent in the same playbook. When we uninstall them they uninstall scsi-target-utils which then makes the playbook reinstall scsi-target-utils causing a loop that results in 2 changed plays every time we run it.
See this commit to see when they were added to ceph-qa-chef: