sonic config bgp listen limit not effect

[tim-rj]

Description

config bgp listen limit 2，show ip bgp su display config is effect,but in fact dynamically BGP neighbors is 3,(after execute clear bgp, still 3)

Steps to reproduce the issue:

1. sonic config dynamically BGP neighbors with DUT4。
   switch1# vtysh
   switch1# configure terminal
   switch1(config)# router bgp 65100
   switch1(config-router)# neighbor PEER peer-group
   switch1(config-router)# neighbor PEER remote-as 100
   switch1(config-router)# bgp listen range 10.0.0.0/16 peer-group PEER
   switch1(config-router)# bgp listen limit 2
2. config bgp listen limit 2
3. clear bgp ,rebuild bgp neighbors
4. show ip bgp su, bgp neighbors is 3

Describe the results you received:
config bgp listen limit 2, dynamically BGP neighbors is 3

Describe the results you expected:
config bgp listen limit 2, dynamically BGP neighbors is 2

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```
    root@switch1:/home/admin# show version
SONiC Software Version: SONiC.201803_rj.0-9e5e2a4-20181128.173206
Distribution: Debian 8.11
Kernel: 3.16.0-5-amd64
Build commit: 9e5e2a4
Build date: Wed Nov 28 17:35:18 UTC 2018
Built by: ngcf@ubuntu01

Docker images:
REPOSITORY TAG IMAGE ID SIZE
docker-orchagent-brcm 201803_rj.0-9e5e2a4-20181128.173206 ff563f8a8a5e 364.6 MB
docker-orchagent-brcm latest ff563f8a8a5e 364.6 MB
docker-teamd 201803_rj.0-9e5e2a4-20181128.173206 2bec314c0cba 356 MB
docker-teamd latest 2bec314c0cba 356 MB
docker-fpm-frr 201803_rj.0-9e5e2a4-20181128.173206 8e8c63535800 360.9 MB
docker-fpm-frr latest 8e8c63535800 360.9 MB
docker-syncd-brcm 201803_rj.0-9e5e2a4-20181128.173206 271c843e1f4d 986.1 MB
docker-syncd-brcm latest 271c843e1f4d 986.1 MB
docker-lldp-sv2 201803_rj.0-9e5e2a4-20181128.173206 e6372670ce81 365.3 MB
docker-lldp-sv2 latest e6372670ce81 365.3 MB
docker-snmp-sv2 201803_rj.0-9e5e2a4-20181128.173206 682b40d6e204 387.9 MB
docker-snmp-sv2 latest 682b40d6e204 387.9 MB
docker-platform-monitor 201803_rj.0-9e5e2a4-20181128.173206 5482ac5f494a 367.2 MB
docker-platform-monitor latest 5482ac5f494a 367.2 MB
docker-router-advertiser 201803_rj.0-9e5e2a4-20181128.173206 f7dabf27a671 348.3 MB
docker-router-advertiser latest f7dabf27a671 348.3 MB
docker-dhcp-relay 201803_rj.0-9e5e2a4-20181128.173206 89e26a55b78d 350.1 MB
docker-dhcp-relay latest 89e26a55b78d 350.1 MB
docker-database 201803_rj.0-9e5e2a4-20181128.173206 c7238159374c 350.6 MB
docker-database latest c7238159374c 350.6 MB

GIT version:
MODULE BRANCH COMMIT_ID VERSION
sonic-swss-common 201803_rj 60a0a29dd09a
sonic-kernel 201803_rj 6cfcef24f4e0
sonic-sairedis 201803_rj 4ac34bb472e8
sonic-swss 201803_rj 3791b9405874
sonic-quagga 201803_rj b497e090787c
sonic-dbsync 201803_rj 1d0b2165e097
sonic-py-swsssdk 201803_rj ca540c9c51e2
sonic-snmpagent 201803_rj 12bc0e0c9843
sonic-ptf 201803_rj aac6efd0a78b
sonic-utilities 201803_rj d3bbeec71330
sonic-platform-common 201803_rj 0a6094670d0c
sonic-platform-daemons 201803_rj 31c007e260ba
sonic-frr 201803_rj 26473f4b87c5
sonic-platform-modules-ruijie master 064c83605b6a
sonic-sai 201803_rj c7c198d7d2cb
sonic-ptf-sairedis 201803_rj aac6efd0a78b
sonic-saithrift-ctypesgen 201803_rj 3d2d98033395
sonic-googletest 201803_rj ec44c6c1675c
sonic-brcm-sai brcm-sai-GA ad131e7a1157
sonic-initramfs-tools 201803_rj 8ec9eca084bf
sonic-libteam master 8c1cea00a219 v1.26
sonic-libteam-debian master da006f226c53 da006f2
sonic-supervisor master 85d0b206928f
sonic-isc-dhcp master 1d74837d0203
sonic-lldpd master 66f8a863e9ae
sonic-libnl3 master b77c0e49cb64 b77c0e49c
sonic-pam_tacplus master 8dddbec2940f v1.4.1
sonic-libnss-tacplus master 19008ab68d9d 19008ab

SDK version:
||/ Name Version Architecture Description
+++-==============================-============-============-==========================================================
ii libopennsl 3.5.0.4 amd64 shared library for broadcom opennsl sdk
ii libopennsl-dev 3.5.0.4 amd64 development library for broadcom opennsl sdk
ii libsaibcm 3.2.1.1 amd64 Switch Abstraction Interface sdk based on Broadcom opennsl
ii opennsl-modules-3.16.0-5-amd64 3.5.0.4 amd64 kernel modules for broadcom opennsl sdk 
```

**Attach debug file `sudo generate_dump`:**

```

config_db.json.txt

```

[pavel-shirshov]

@tim-rj We found the issue too. We decided don't solve it in quagga for now. If this is critical for you, can you please create PR fixing the issue?

Thanks