fusefs: annotate more file descriptor leaks in the tests

The fusefs tests intentionally leak file descriptors. Annotate all of
the leakages in order to hopefully pacify Coverity.

Reported by: Coverity (20 different CIDs)
Sponsored by: Axcient

(cherry picked from commit 4ac4b12699fd423165a0ac0d05630a1fae022bbb)