path_test: Correct the kevent test

Perhaps surprisingly, and contrary to the expectations of
path_test:path_event, NOTE_LINK events are not raised when a file is
unlinked. Prior to commit bf13db086b84, the test happened to work
because unlinking the file would cause the vnode to be recycled, and
EVFILT_VNODE knotes deliver an event with EV_EOF set when the vnode is
doomed. Since the test did not verify the note type, the test
succeeded. After commit bf13db086b84, the vnode is not recycled after
being unlinked and so the test hangs.

Fix the test by waiting for NOTE_DELETE instead, and check that we got
the note that we expected.

Reported by: Jenkins
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 333f668468f0675e1e001f6fcc506e901e58c36e)