Fix UnboundLocalError in KexecSuite._wait_for_reconnect

[Copilot]

KexecSuite.verify_kexec_reboot_direct crashes with UnboundLocalError: cannot access local variable 'current_boot_time' because current_boot_time is only assigned inside the try block — when kexec drops the SSH connection (the expected path), an exception is caught and the variable is never set, causing failures on subsequent references.

Fix

Initialize current_boot_time = last_boot_time before the reconnect loop, matching the identical pattern in lisa/tools/reboot.py:

# Before
timer = create_timer()
connected: bool = False
tried_times: int = 0
while ...:
    try:
        node.close()
        current_boot_time = self._get_last_boot_time(node)  # never reached on disconnect
        ...
    except Exception:
        ...
    log.debug(f"reconnected with uptime: {current_boot_time}")  # UnboundLocalError here

# After
timer = create_timer()
connected: bool = False
tried_times: int = 0
current_boot_time = last_boot_time  # safe default before loop
while ...:
    ...

The initialization also ensures the post-loop if last_boot_time == current_boot_time check correctly identifies a failed reboot when reconnection never succeeded.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.