Fix issues in Logdump module

[kishore-sn]

          There are 3 strncmp s to check a command. It looks not good.

Because the data is a just character, how about using switch / case?

Here you added the else case to check stop first. How about adding it at the read function as well? Because it's the same.

Originally posted by @sunghan-chang in #6394 (comment)

Line number 292 and 524