CN crashes during service chain introspect when there's a deleted RI

CN crashes during service chain introspect when there's a deleted RI.

The core is placed at
/cs-shared/bugs/1717231 on any blr shell server

bhushana@mayamruga:~/Documents/technical/bugs/1717231$ pwd
/home/bhushana/Documents/technical/bugs/1717231
bhushana@mayamruga:~/Documents/technical/bugs/1717231$ ls -lrt
total 579128
-rwxrwxrwx 1 bhushana bhushana 225251328 Sep 27 12:10 core.contrail-contro.29945.nodei21.1506492734
-rwxrwxrwx 1 bhushana bhushana 367772744 Sep 27 12:11 contrail-control
bhushana@mayamruga:~/Documents/technical/bugs/1717231$

BT
==
(gdb) bt
#0 BgpInstanceConfig::service_chain_info (this=0x0, family=family@entry=Address::INET) at controller/src/bgp/bgp_config.cc:360
#1 0x00000000006a13af in FillServiceChainInfo (family=Address::INET, rtinstance=0x2b660c038d60, info=..., search_expr=..., search_string="") at controller/src/bgp/routing-instance/show_service_chaining.cc:42
#2 BgpShowHandler<ShowServiceChainReq, ShowServiceChainReqIterate, ShowServiceChainResp, ShowServicechainInfo>::CallbackCommon (bsc=bsc@entry=0x7ffd5d5d7720, data=data@entry=0x2b661c009740) at controller/src/bgp/routing-instance/show_service_chaining.cc:78
#3 0x00000000006a275e in BgpShowHandler<ShowServiceChainReq, ShowServiceChainReqIterate, ShowServiceChainResp, ShowServicechainInfo>::Callback (sr=sr@entry=0x2b661400e870, ps=..., stage=stage@entry=0, instNum=instNum@entry=0, data=data@entry=0x2b661c009740)
    at controller/src/bgp/bgp_show_handler.h:172
#4 0x000000000069b1dc in operator()<bool, bool (*)(const Sandesh*, RequestPipeline::PipeSpec, int, int, RequestPipeline::InstData*), boost::_bi::list5<const Sandesh*&, const RequestPipeline::PipeSpec&, int&, int&, RequestPipeline::InstData*&> > (this=<optimized out>,
    f=<optimized out>, a=<synthetic pointer>) at /usr/include/boost/bind/bind.hpp:515
#5 operator()<const Sandesh*, const RequestPipeline::PipeSpec, int, int, RequestPipeline::InstData*> (a5=<synthetic pointer>, a4=<synthetic pointer>, a3=<synthetic pointer>, a2=..., a1=<synthetic pointer>, this=<optimized out>)
    at /usr/include/boost/bind/bind_template.hpp:174
#6 boost::detail::function::function_obj_invoker5<boost::_bi::bind_t<bool, bool (*)(Sandesh const*, RequestPipeline::PipeSpec, int, int, RequestPipeline::InstData*), boost::_bi::list5<boost::arg<1>, boost::arg<2>, boost::arg<3>, boost::arg<4>, boost::arg<5> > >, bool, Sandesh const*, RequestPipeline::PipeSpec const&, int, int, RequestPipeline::InstData*>::invoke (function_obj_ptr=..., a0=0x2b661400e870, a1=..., a2=0, a3=0, a4=0x2b661c009740) at /usr/include/boost/function/function_template.hpp:132
#7 0x0000000000d9a4d3 in operator() (a4=<optimized out>, a3=<optimized out>, a2=<optimized out>, a1=..., a0=<optimized out>, this=<optimized out>) at /usr/include/boost/function/function_template.hpp:767
#8 RequestPipeline::PipeImpl::RunInstance (this=<optimized out>, instNum=<optimized out>) at tools/sandesh/library/cpp/request_pipeline.cc:189
#9 0x0000000000d9baf5 in RequestPipeline::StageWorker::Run (this=0x2b661c06be00) at tools/sandesh/library/cpp/request_pipeline.cc:84
#10 0x00000000006fff37 in TaskImpl::execute (this=0x2b65b1aaaf40) at controller/src/base/task.cc:277
#11 0x00002b65a999cb3a in ?? ()
#12 0x00002b65b1a73f28 in ?? ()
#13 0x00002b65b1a73f40 in ?? ()
#14 0x0000000000000001 in ?? ()
#15 0x00002b65b19d3c80 in ?? ()
#16 0x00002b65b1a73f28 in ?? ()
#17 0x0000000000000000 in ?? ()