…or ipv6 address (#4852)

	-What I did
	Snmpagentaddress now support upper letters input for ipv6 address
	Fix some grammer mistakes

	-How I did
	Convert all agentip to lower letters to match netifaces addresses
	delete ; after break, convert addfress to address

	-How to verify it
	'sudo config snmpagentaddress add FC00:1::32 -v mgmt'
	The ipv6 address can be obtained by command 'sudo ifconfig'

-What I did
Snmpagentaddress now support upper letters input for ipv6 address

-How I did
Compare the lower letter of input and netifaces addresses

-How to verify it
'sudo config snmpagentaddress add FC00:1::32 -v mgmt'
The ipv6 address can be obtained by command 'sudo ifconfig'