fixup! utils.adb_shell: Improve stability (Py3)

Author: pietos01-arm

devlib/utils/android.py

@@ -439,7 +439,7 @@ def adb_shell(device, command, timeout=None, check_exit_code=False,
     # command failed (https://code.google.com/p/android/issues/detail?id=3254).
     # Homogenise this behaviour by running the command then echoing the exit
     # code.
-    parts[-1] += r' ; echo "\n$?"'
+    parts[-1] += ' ; echo "\n$?"'
     try:
         raw_output, _ = check_output(parts, timeout, shell=False, combined_output=True)
     except subprocess.CalledProcessError as e: