zebra: fix advertise svi ip as macip route

zebra: fix advertise svi ip as macip route

PR #3745 added EVPN feature to advertise individual
SVI-IPs as MAC-IP routes.
Fix a condition in zebra to send MAC and IP pair
to bgpd when the feature is enabled.

Testing Done:

Originator VTEP:
TORC11:~# ip -br addr show VxU-1002
VxU-1002         UP             45.0.2.2/24 2001:fee1:0:2::2/64

show bgp l2vpn evpn vni 1004
VNI: 1004 (known to the kernel)
  Type: L2
  Tenant-Vrf: default
  RD: 27.0.0.11:3
  Advertise-svi-macip : Yes
  Import Route Target:
    10:1004
  Export Route Target:
    10:1004

Remote vtep evpn route output for 45.0.4.2:

BGP routing table entry for 27.0.0.11:3:[2]:[0]:[48]:[00:02:00:00:00:2f]:[32]:[45.0.4.2]
Paths: (2 available, best #1)
  Advertised to non peer-group peers:
  MSP1(uplink-1) MSP2(uplink-2)
  Route [2]:[0]:[48]:[00:02:00:00:00:2f]:[32]:[45.0.4.2] VNI 1004
  64435 65546
    36.0.0.11 from MSP1(uplink-1) (27.0.0.9)
      Origin IGP, valid, external, bestpath-from-AS 64435, best (First path received)
      Extended Community: RT:10:1004 ET:8
      Last update: Thu Aug  8 18:09:13 2019

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>