close more file descriptors on exec

Don't inherit the --status and --ifconfig-pool-persist, and on Linux
the epoll(7), file descriptors to scripts and other processes that
may be forked by plugins.

Signed-off-by: Heiko Hund <heiko.hund@sophos.com>
Acked-by: David Sommerseth <davids@redhat.com>
Message-Id: 1359728354-9405-1-git-send-email-heiko.hund@sophos.com
URL: http://article.gmane.org/gmane.network.openvpn.devel/7312
Signed-off-by: David Sommerseth <davids@redhat.com>
(cherry picked from commit 09ee4192b1d16bbd7c3c138cc2d46760a11797bf)