Remove telnet Output_log parameter

The puppet telnet util opened an output log by default with a predictable name.
This left the log open to a write-through symlink attack as the puppet user.
This fix addresses that by removing the Output_log parameter from the
Net::Telnet::new call. Without the parameter, Net::Telnet defaults to no output
logging. The same is true for the dump_log parameter. The spec test for telnet
has been updated to test and ensure that no files are opened during connect. It
also stubs the TCPSocket for the telnet connection so that no connection is
attempted if @transport.connect isn't stubbed.