Revert "Revert "epoll: fix up lock ordering issues""

This reverts commit 408a982f3f2fbd4a3aaddafb60233909eb6b7b83.

I never see the build issue mentioned by Nadav. I tested this patch with
tomcat + nio connector which uses epoll intensively and I did not see any
issue.

Signed-off-by: Asias He <asias@cloudius-systems.com>
epoll: Get rid of registered_epoll

After commit 3082e79f14339be0737fed55f2d3ab3f8c260983 (epoll: a real
epoll), our epoll is not on top of poll any more. last_poll_wake_count
is not used. Remove the leftover.

Signed-off-by: Asias He <asias@cloudius-systems.com>
poll: Remove poll_wake_count

After commit 3082e79f14339be0737fed55f2d3ab3f8c260983 (epoll: a real
epoll), our epoll is not on top of poll any more. We can remove hacks
for implementing epoll() over poll().

Signed-off-by: Asias He <asias@cloudius-systems.com>
epoll: Drop events_epoll_to_poll and friends

Signed-off-by: Asias He <asias@cloudius-systems.com>
epoll: Drop leftover comments

epoll is not implemented on top of poll any more. Remove incorrect
comments.

Signed-off-by: Asias He <asias@cloudius-systems.com>
do not remove
ci