use "\n" instead of semicolon to separate redis commands in a c++ string

[a114j0y]

replace ";" with "\n" when concatenating multiple redis cmds

[prsunny]

@liuh-80 , @qiluo-msft , can you merge this?

[yuezhoujk]

/azp run Azure.sonic-swss-common

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[lguohan]

@qiluo-msft , @liuh-80 , @yuezhoujk , please explain motivation of such change.

[a114j0y]

@qiluo-msft , @liuh-80 , @yuezhoujk , please explain motivation of such change.

We see such an exception when running the testcase in the azure pipeline:

C++ exception with description "RedisReply catches system_error: command: *3\r\n$6\r\nSCRIPT\r\n$4\r\nLOAD\r\n$52\r\nredis.call('PUBLISH', 'ROUTE_TABLE_CHANNEL@0', 'G');\r\n, reason: Expected to get redis type 1 got type 3, err: NON-STRING-REPLY: Input/output error: Input/output error" thrown in SetUp().

which indicates that the redis server fails to do SCRIPT LOAD, although it works on our end.

We checked the c++ string m_luaPub that is to be loaded into a redis script:
m_luaPub += "redis.call('PUBLISH', '" + channel + "', 'G');";

it could be successfully loaded into script on our end, but throws exception in the azure pipeline.