ssh: Fix command line echoing

Command line echoing was disabled, but that disabling did not take
effect. Another part of devlib was still expecting command lines to be
echoed. That is fixed by disabling echoing when creating pxssh
connection, and removing the code that expected the line to be echoed.

devlib/utils/ssh.py

@@ -63,7 +63,7 @@ def ssh_get_shell(host, username, password=None, keyfile=None, port=None, timeou
                 raise ValueError('keyfile may not be used with a telnet connection.')
             conn = TelnetPxssh(original_prompt=original_prompt)
         else:  # ssh
-            conn = pxssh.pxssh()
+            conn = pxssh.pxssh(echo=False)
 
         try:
             if keyfile:
@@ -278,15 +278,11 @@ def _execute_and_wait_for_prompt(self, command, timeout=None, as_root=False, str
                 logger.debug(command)
             self._sendline(command)
         timed_out = self._wait_for_prompt(timeout)
-        # the regex removes line breaks potential introduced when writing
-        # command to shell.
         if sys.version_info[0] == 3:
             output = process_backspaces(self.conn.before.decode(sys.stdout.encoding or 'utf-8', 'replace'))
         else:
             output = process_backspaces(self.conn.before)
-        output = re.sub(r'\r([^\n])', r'\1', output)
-        if '\r\n' in output: # strip the echoed command
-            output = output.split('\r\n', 1)[1]
+
         if timed_out:
             self.cancel_running_command()
             raise TimeoutError(command, output)