[fpmsyncd] Added CLI for Fpmsyncd Next Hop Table Enhancement

[ntt-omw]

Why I did it

Implementing code changes for https://github.com/sonic-net/SONiC/pull/1425

How to verify it

enable/disable nexthop group feature

• Klish will call REST API to configure feature next-hop-group enable.
• FEATURE|nexthop_group will be created in CONFIG_DB
  • template zebra.conf.j2 will generate zebra.conf with fpm use-next-hop-groups if FEATURE|nexthop_group exists in CONFIG_DB. Else, it will generate zebra.conf with no fpm use-next-hop-groups (default behavior)
• Do config save comman and write to /etc/sonic/config_db.json
• restart SONiC: virsh reboot sonic-nhg
• /etc/frr/zebra.conf has fpm use-next-hop-groups instead of no fpm use-next-hop-groups

Klish CLI for feature nexthop_group

• Enable: sonic(config)# feature next-hop-group enable
• Disable: sonic(config)# no feature next-hop-group

Enable

admin@sonic:~$ sonic-cli

sonic# configure terminal

sonic(config)#
  end        Exit to EXEC mode
  exit       Exit from current mode
  feature    Configure additional feature
  interface  Select an interface
  ip         Global IP configuration subcommands
  mclag      domain
  no         To delete / disable commands in config mode

sonic(config)# feature
  next-hop-group  Next-hop Groups feature

sonic(config)# feature next-hop-group
  enable  Enable Next-hop Groups feature

sonic(config)# feature next-hop-group enable
  <cr>

Disable

sonic(config)# no
  feature  Disable additional feature
  ip       Global IP configuration subcommands
  mclag    domain

sonic(config)# no feature
  next-hop-group  Disable Next-hop Groups feature

sonic(config)# no feature next-hop-group
  <cr>

[nakano-omw]

Hi @ayelrod It has been reviewed in Routing WG. Could we merge the PR ?