test: add command to 'Boot fail' message

When a timeout occurs while executing a command a 'Boot fail' message is
written and testing is stopped. The user is left in the dark about the
failure cause.

    ! _pytest.outcomes.Exit: Boot fail: Marking connection bad - no other tests will run !

Add the executed command to the message.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/test/py/u_boot_console_base.py b/test/py/u_boot_console_base.py
index 070ad28..7eaceb3 100644
--- a/test/py/u_boot_console_base.py
+++ b/test/py/u_boot_console_base.py
@@ -346,7 +346,8 @@
                              f"Lab failure: Timeout executing '{cmd}'", True)
             raise
         except BootFail as exc:
-            handle_exception(self.config, self, self.log, exc, 'Boot fail',
+            handle_exception(self.config, self, self.log, exc,
+                             f"'Boot fail '{cmd}'",
                              True, self.get_spawn_output())
             raise
         finally: