Also some typos were fixed

- Why I did it

1. Fix an error which causes bgpcfgd crash on invalid ip address. Before the fix we had an issue here. When either loopback ipv4 or ipv6 addresses were already set and bgpcfgd received another "SET" message for already set ip loopback address, bgpcfgd will send syslog message about ambiguous ip address (despite the fact that the address is good) and crash of bgpcfgd. With this change this behavior is changed: if we receive ip address and this ip address is already set, bgpcfgd will send this message to the syslog and return from the handler.

2. Fix typos

- How I did it
Return from the handler on invalid ip address

- How to verify it
Build an image, run on your dut. Add an interface entry with invalid ip address. bgpcfgd should not crash.

admin@str-s6100-acs-1:~$ redis-cli 
127.0.0.1:6379> select 4
OK
127.0.0.1:6379[4]> keys L*
1) "LOOPBACK_INTERFACE|Loopback0|FC00:1::32/128"
2) "LOOPBACK_INTERFACE|Loopback0|10.1.0.32/32"
127.0.0.1:6379[4]> hgetall "LOOPBACK_INTERFACE|Loopback0|10.1.0.32/32"
1) "NULL"
2) "NULL"
127.0.0.1:6379[4]> hset "LOOPBACK_INTERFACE|Loopback0|10.1.0.32/32" NULL NULL
(integer) 0
127.0.0.1:6379[4]> hset "LOOPBACK_INTERFACE|Loopback0|FC00:1::32/128" NULL NULL
(integer) 0

admin@str-s6100-acs-1:~$ sudo tail -F /var/log/syslog | grep bgpcfgd


Jul 27 18:54:32.241152 str-s6100-acs-1 INFO bgp#bgpcfgd: Update command is not supported for set src templates. lo_ip='10.1.0.32'

Jul 27 18:54:57.701735 str-s6100-acs-1 INFO bgp#bgpcfgd: Update command is not supported for set src templates. lo_ip='FC00:1::32'

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

• 201811
• 201911
• 202006

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)