[frr] prefers ipv6 link-local as next hop address

[stepanblyschak]

Description
After a change to use seperated configuration mode, frr prefers to use link-local ipv6 addresses as nexthop address. This is behavior change comparing to quagga and also orchagent fails to proceses such routes and takes 100% cpu, because tries to insert such route in an endless loop

Steps to reproduce the issue:

1. Run public image 990 on t0/t1/t1-lag topologies
2. Execute "show ipv6 route"

Describe the results you received:
In "show ipv6 route" output you can see link-local addresses are used as next hop addresses

Describe the results you expected:
Either change frr to prefer global ipv6 or make link-local next hop be processed correctly by orchagent

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

**Output of `show version`:**

```

SONiC Software Version: SONiC.HEAD.990-9dc1cc76
Distribution: Debian 9.9
Kernel: 4.9.0-8-2-amd64
Build commit: 9dc1cc7
Build date: Sun Jun 9 03:14:52 UTC 2019
Built by: johnar@jenkins-worker-4

Platform: x86_64-mlnx_msn2010-r0
HwSKU: ACS-MSN2010
ASIC: mellanox
Serial Number: MT1749X10061
Uptime: 15:27:17 up 2 min, 1 user, load average: 7.28, 3.36, 1.29

Docker images:
REPOSITORY TAG IMAGE ID SIZE
docker-syncd-mlnx HEAD.990-9dc1cc76 1cddd3463b02 369MB
docker-syncd-mlnx latest 1cddd3463b02 369MB
docker-lldp-sv2 HEAD.990-9dc1cc76 4b03a7a67280 299MB
docker-lldp-sv2 latest 4b03a7a67280 299MB
docker-dhcp-relay HEAD.990-9dc1cc76 8f06c5b8462d 288MB
docker-dhcp-relay latest 8f06c5b8462d 288MB
docker-database HEAD.990-9dc1cc76 09aa9e4be928 281MB
docker-database latest 09aa9e4be928 281MB
docker-snmp-sv2 HEAD.990-9dc1cc76 f82ee7831a47 313MB
docker-snmp-sv2 latest f82ee7831a47 313MB
docker-orchagent HEAD.990-9dc1cc76 ec34623eb382 319MB
docker-orchagent latest ec34623eb382 319MB
docker-teamd HEAD.990-9dc1cc76 ebe6b0ef5acc 301MB
docker-teamd latest ebe6b0ef5acc 301MB
docker-sonic-telemetry HEAD.990-9dc1cc76 d135f140b0ae 302MB
docker-sonic-telemetry latest d135f140b0ae 302MB
docker-router-advertiser HEAD.990-9dc1cc76 eececba36c7f 280MB
docker-router-advertiser latest eececba36c7f 280MB
docker-platform-monitor HEAD.990-9dc1cc76 b7bcd1686023 326MB
docker-platform-monitor latest b7bcd1686023 326MB
docker-fpm-frr HEAD.990-9dc1cc76 707e7322552e 309MB
docker-fpm-frr latest 707e7322552e 309MB
```

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

```
(paste your output here)
```

[stephenxs]

I'm just curious that why neighsync disables link-local address from notifying orchagent. is there any reason behind?

[lguohan]

link-local is not supported yet.

[nazariig]

@lguohan do we have any estimates for this: sonic-net/sonic-swss#437