fix(console): skip extra newline after username in login_stage_2()

The login loop in SSHConsoleConn.login_stage_2() sends an unconditional
write_channel(RETURN) at the bottom of every iteration. After the username
is sent and user_sent is set to True, the loop falls through to this
write_channel, sending a blank newline to the DUT before the Password:
prompt is read.

The DUT receives the blank newline as the password input, causing
authentication to fail. Linux pam_faildelay then enforces a 3-second
delay before responding with Login incorrect. The test framework times
out within this 3-second window, closes the connection, and retries -
all three attempts fail the same way.

Fix: add continue after user_sent = True so the loop restarts at the
top and waits for the Password: prompt before taking any further action.

Root cause confirmed via live manual test on bjw-can-7060-1:
- Sending empty Enter at Password: prompt -> 3-second silence -> Login incorrect
- Normal login with correct password succeeds in under 1 second
- Pass rate of dut_console/test_escape_character.py was 2.6% due to this race

Author: lipxu

tests/common/connections/ssh_console_conn.py

@@ -133,6 +133,7 @@ def login_stage_2(self,
                     output = self.read_channel()
                     return_msg += output
                     user_sent = True
+                    continue  # Skip loop-bottom write_channel(RETURN); wait for Password: prompt next iteration
 
                 # Search for password pattern / send password
                 if user_sent and not password_sent and re.search(pwd_pattern, output, flags=re.I):