Select groups without any buckets for remote MIPs

Select groups without any buckets for remote MIPs

Issue-1:
--------
Inconsistency observed in table-21 flows. For remote IPv4/IPv6 MIPs,
traffic for fixed IPs are sent directly to table-220. But
traffic for remote learnt/MIPs are sent to groups.

Issue-2:
--------
Sporadic issue wherein when MIPs are learnt, perform delete and add
Transport zone (ITM). The corresponding groups referred in table-21
flows for remote MIPs have Select Groups without any buckets in one
of the DPN.

Solution for both 1 and 2:
--------------------------
+ Remote learnt/MIPs were treated as extra routes, hence were sent to
  load-balancing groups (Select). With this fix now, even for remote
  learnt/MIPs, traffic is directly sent to table-220 from table-21.

+ Refactored code to minimize datastore reads.

JIRA: NETVIRT-1553

Change-Id: Idb71cc6e5e2ce3eb812e36e51a0987a204d778dc
Signed-off-by: Somashekar Byrappa <somashekar.b@altencalsoftlabs.com>