[sonic boot] disable dhcp during boot up, until updategraph service is running (#2316)

* [sonic] disable management port eth0 during boot up

Signed-off-by: Ying Xie <ying.xie@microsoft.com>

* [updategraph] enable dhcp client on management port eth0

Signed-off-by: Ying Xie <ying.xie@microsoft.com>

files/image_config/interfaces/init_interfaces

@@ -5,6 +5,4 @@
 auto lo
 iface lo inet loopback
 #
-# The management network interface
-auto eth0
-iface eth0 inet dhcp
+# Disable the management network interface during boot up

files/image_config/updategraph/updategraph

@@ -77,6 +77,10 @@ fi
 ACL_URL=$acl_src
 
 if [ "$src" = "dhcp" ]; then
+    # Enable dhcp client on management port eth0
+    /sbin/dhclient -4 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0 &
+    disown
+
     while [ ! -f /tmp/dhcp_graph_url ]; do
         echo "Waiting for DHCP response..."
         sleep 1