webservd: whitelist epoll_create1 in seccomp filter policy

libevent has been upgraded to 2.1.8 (CL:443260), which uses the
epoll_create1 syscall. This CL whitelists the epoll_create1 syscall in
the seccomp filter policy for webservd.

BUG=b:35934451
TEST=Verify that webservd runs properly.

Change-Id: Ifa985d1cf663cf52109c5298bb28458e6b3846f0
Reviewed-on: https://chromium-review.googlesource.com/449964
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Srinivasa duvvuri <sduvvuri@chromium.org>

webservd/usr/share/filters/webservd-seccomp.policy

diff --git a/webservd/usr/share/filters/webservd-seccomp.policy b/webservd/usr/share/filters/webservd-seccomp.policy
index 00a9ceb..4567d9e 100644
--- a/webservd/usr/share/filters/webservd-seccomp.policy
+++ b/webservd/usr/share/filters/webservd-seccomp.policy
@@ -25,6 +25,7 @@
 creat: 1
 dup: 1
 epoll_create: 1
+epoll_create1: 1
 epoll_ctl: 1
 epoll_wait: 1
 exit_group: 1