[mclaglink] fix acl out ports

[globaltrouble]

What I did

Delete redundant copy to remove string duplication.

Why I did it

isolate_dst_port is initialized as blank string,

    string isolate_dst_port;

then data is inserted into the begining

   isolate_dst_port.insert(0, (const char*)cur, op_hdr->op_len);
   // now isolate_dst_port = "PortChannel0001,Ethernet0"

then isolate_dst_port is printed to logs:

        SWSS_LOG_NOTICE("set port isolate, src port: %s, dst port: %s",
                isolate_src_port.c_str(), isolate_dst_port.c_str());

Logs:

Nov 12 15:45:40.848696 sonic NOTICE iccpd#mclagsyncd: :- setPortIsolate: set port isolate, src port: PortChannel0002, dst port: PortChannel0001,Ethernet0

neither op_hdr, neither isolate_dst_port changed, but same string from op_hdr is inserted into the isolate_dst_port.

    isolate_dst_port.insert(0, (const char*)cur, op_hdr->op_len);
    // now isolate_dst_port = "PortChannel0001,Ethernet0PortChannel0001,Ethernet0"

after splitting the string by , first entry is skipped, as it starts with PortChannel, and final attr is Ethernet0PortChannel0001,Ethernet0

Logs:

Nov 12 15:45:41.659344 sonic ERR swss#orchagent: :- doAclRuleTask: Unknown or invalid rule attribute 'OUT_PORTS : Ethernet0PortChannel0001,Ethernet0'

How I verified it

Configure MC-LAG as described in issue #1938 .

[globaltrouble]

@prsunny could you please review it?

[gechiang]

@Praveen-Brcm
The change looks good to me. But like to get your comment on this fix in case I may have missed something.
Can you help take a look at this change please.
Thanks!

[globaltrouble]

@gechiang @Praveen-Brcm looks like the whole function does not work at all because it consists of 2 cases: port isolation group and ACL isolation.
ACL isolation does not work due to this issue.
Port isolation does not work because it use env platform to check its condition and mclagsyncd work inside iccpd container and iccpd container does not set platform env so code in port isolation branch will never be executed.

[Praveen-Brcm]

Changes looks good. Thanks.

[globaltrouble]

@gechiang , @prsunny could you please review it?

[prsunny]

@gechiang , could you please sign-off and merge this PR?