timers: don't close interval timers when unrefd

This change fixes a regression introduced by commit
0d051238be2e07e671d7d9f4f444e0cc1efadf1b, which contained a typo that
would cause every unrefd interval to fire only once.

Fixes #8900.

Reviewed-By: Timothy J Fontaine <tjfontaine@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-by: Trevor Norris <trev.norris@gmail.com>
src: re-add 1024-bit SSL certs removed by f9456a2

this fixes a problem where connecting to AWS services
would report an untrusted cert error.

Fixes: https://github.com/joyent/node/issues/8894
PR-URL: https://github.com/joyent/node/pull/8904
Reviewed-By: Timothy J Fontaine <tjfontaine@gmail.com>
Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
timers: don't mutate unref list while iterating it

Commit 934bfe23a16556d05bfb1844ef4d53e8c9887c3d had introduced a
regression where node would crash trying to access a null unref timer if
a given unref timer's callback would remove other unref timers set to
fire in the future.

More generally, it makes the unrefTimeout function more solid by not
mutating the unrefList while traversing it.

Fixes #8897.