Remove the meaningless status message in status code option.

status-message is UTF-8 encoded text string suitable for display to the
end user, which is not useful for Dhcp6client's decision on if it should
ignore the current reply, just skip the status-message parsing for the
top level status code option.

Bug: 315069348
Test: atest NetworkStackTests
Change-Id: If231729abf6294acbab4c16b0c7a8665ad588548
2 files changed