Inject an init script

It's very basic for the moment

Ref #1089

gns3server/modules/docker/resources/init.sh

@@ -0,0 +1,46 @@
+#!/bin/sh
+#
+# Copyright (C) 2016 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#
+# This script is injected into the container and launch before
+# the start command of the container
+#
+
+# Wait 2 seconds to settle the network interfaces
+sleep 2
+
+# /etc/hosts
+[ -s /etc/hosts ] || cat > /etc/hosts << __EOF__
+127.0.1.1	$HOSTNAME
+127.0.0.1	localhost
+::1	localhost ip6-localhost ip6-loopback
+fe00::0	ip6-localnet
+ff00::0	ip6-mcastprefix
+ff02::1	ip6-allnodes
+ff02::2	ip6-allrouters
+__EOF__
+
+# configure loopback interface
+ip link set dev lo up
+
+# configure eth interfaces
+sed -n 's/^ *\(eth[0-9]*\):.*/\1/p' < /proc/net/dev | while read dev; do
+	ip link set dev $dev up
+done
+
+# continue normal docker startup
+/bin/sh -c "$@"