Fix dynamic buffer bug occuring in rare condition (sonic-net#1678)

What I did
Bug:
The buffermgrd can keep adding suffix to the buffer pool reference if the buffer pool isn't found when it is being referenced. In most of the cases, it's caused by wrong configuration.
Cause:
In handleBufferProfileTable, the value of each field is designated by a (lvalue) reference to the object in the tuple, which means the object in the tuple will be changed if the value is changed in the function.
Fix:
Pass the value of each field by value instead of reference.

- Why I did it
Fix bug.

- How I verified it
Manually test.

Signed-off-by: Stephen Sun stephens@nvidia.com

Author: stephenxs

cfgmgr/buffermgrdyn.cpp

@@ -1609,8 +1609,8 @@ task_process_status BufferMgrDynamic::handleBufferProfileTable(KeyOpFieldsValues
         }
         for (auto i = kfvFieldsValues(tuple).begin(); i != kfvFieldsValues(tuple).end(); i++)
         {
-            string &field = fvField(*i);
-            string &value = fvValue(*i);
+            const string &field = fvField(*i);
+            string value = fvValue(*i);
 
             SWSS_LOG_DEBUG("field:%s, value:%s", field.c_str(), value.c_str());
             if (field == buffer_pool_field_name)