[bgp]: start bgp service after interfaces-config service (sonic-net#3702)

interfaces-config service configures lo address. If bgp service
starts before lo address is configured, then following config
in zebra will not be applied.

route-map RM_SET_SRC permit 10
 set src 10.1.0.32

The adds a few seconds delay in bgp service start

Author: lguohan

files/build_templates/bgp.service.j2

@@ -1,7 +1,7 @@
 [Unit]
 Description=BGP container
 Requires=updategraph.service
-After=updategraph.service
+After=updategraph.service interfaces-config.service
 Before=ntp-config.service
 
 [Service]