modetest: gamma cleanups (partial from !58)
Supersedes !58 (closed)
Stop spamming ENOSYS
if the legacy gamma API isn't available for resetting either (commit 2 from !58 (closed)). Also add a comment to explain why no blob is created in the } else {
branch, in favour of always creating the blob per the first commit in !58 (closed) (which has been dropped).