Add .gitignore entries for recent tests
/test/poll-cancel-ton
/test/poll-link
/test/poll-many
+/test/poll-ring
/test/poll-v-poll
/test/probe
/test/read-write
/test/register-restrictions
/test/rename
/test/ring-leak
+/test/ring-leak2
/test/self
/test/send_recv
/test/send_recvmsg
/test/stdout
/test/submit-reuse
/test/teardowns
+/test/thread-exit
/test/timeout
/test/timeout-new
/test/timeout-overflow
