[dhcp-relay] Reduce Calls to SONiC Cfggen

[tahmed-dev]

Calls to sonic-cfggen is CPU expensive. This PR reduces calls to
sonic-cfggen to one call during startup when starting dhcp-relay
service.

singed-off-by: Tamer Ahmed [email protected]

- Why I did it
Reduce time required when invoking dhcp-relay

- How I did it
Used template batch mode to batch together three calls into one call to sonic-cfggen

- How to verify it

root@str-s6000-acs-14:/# time ./docker_init_old.sh

real	0m5.548s
user	0m4.370s
sys	0m0.756s
root@str-s6000-acs-14:/# time ./docker_init_new.sh

real	0m1.611s
user	0m1.346s
sys	0m0.221s
root@str-s6000-acs-14:/# diff /etc/supervisor/conf.d/docker-dhcp-relay.supervisord.conf.old /etc/supervisor/conf.d/docker-dhcp-relay.supervisord.conf.new 
root@str-s6000-acs-14:/# diff /usr/bin/wait_for_intf.sh.old /usr/bin/wait_for_intf.sh.new 
root@str-s6000-acs-14:/# diff /tmp/port-name-alias-map.txt.old /tmp/port-name-alias-map.txt.new 
1,32c1,33
< Ethernet8 fortyGigE0/8
< Ethernet0 fortyGigE0/0
< Ethernet4 fortyGigE0/4
< Ethernet108 fortyGigE0/108
< Ethernet100 fortyGigE0/100
< Ethernet104 fortyGigE0/104
< Ethernet96 fortyGigE0/96
< Ethernet124 fortyGigE0/124
< Ethernet120 fortyGigE0/120
< Ethernet92 fortyGigE0/92
< Ethernet28 fortyGigE0/28
< Ethernet52 fortyGigE0/52
< Ethernet56 fortyGigE0/56
< Ethernet76 fortyGigE0/76
< Ethernet72 fortyGigE0/72
< Ethernet32 fortyGigE0/32
< Ethernet16 fortyGigE0/16
< Ethernet36 fortyGigE0/36
< Ethernet12 fortyGigE0/12
< Ethernet88 fortyGigE0/88
< Ethernet24 fortyGigE0/24
< Ethernet116 fortyGigE0/116
< Ethernet80 fortyGigE0/80
< Ethernet112 fortyGigE0/112
< Ethernet84 fortyGigE0/84
< Ethernet48 fortyGigE0/48
< Ethernet44 fortyGigE0/44
< Ethernet40 fortyGigE0/40
< Ethernet64 fortyGigE0/64
< Ethernet60 fortyGigE0/60
< Ethernet20 fortyGigE0/20
< Ethernet68 fortyGigE0/68
---
> Ethernet0 fortyGigE0/0 
> Ethernet4 fortyGigE0/4 
> Ethernet8 fortyGigE0/8 
> Ethernet12 fortyGigE0/12 
> Ethernet16 fortyGigE0/16 
> Ethernet20 fortyGigE0/20 
> Ethernet24 fortyGigE0/24 
> Ethernet28 fortyGigE0/28 
> Ethernet32 fortyGigE0/32 
> Ethernet36 fortyGigE0/36 
> Ethernet40 fortyGigE0/40 
> Ethernet44 fortyGigE0/44 
> Ethernet48 fortyGigE0/48 
> Ethernet52 fortyGigE0/52 
> Ethernet56 fortyGigE0/56 
> Ethernet60 fortyGigE0/60 
> Ethernet64 fortyGigE0/64 
> Ethernet68 fortyGigE0/68 
> Ethernet72 fortyGigE0/72 
> Ethernet76 fortyGigE0/76 
> Ethernet80 fortyGigE0/80 
> Ethernet84 fortyGigE0/84 
> Ethernet88 fortyGigE0/88 
> Ethernet92 fortyGigE0/92 
> Ethernet96 fortyGigE0/96 
> Ethernet100 fortyGigE0/100 
> Ethernet104 fortyGigE0/104 
> Ethernet108 fortyGigE0/108 
> Ethernet112 fortyGigE0/112 
> Ethernet116 fortyGigE0/116 
> Ethernet120 fortyGigE0/120 
> Ethernet124 fortyGigE0/124 
> 
root@str-s6000-acs-14:/# 

- Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006