Currently, if smartctl is not found by IPA, it will silently skip ATA
secure erase and proceed to shred (if enabled). This is supposedly for
backwards compatibility, but is quite hard to diagnose.
This change adds a warning message to make it more obvious what is
happening.
TrivialFix
Change-Id: I03a381e99de79f201ec7e9a388777c3d48457e93