Fix a format mismatch in IMMS#MSG_HARD_KEYBOARD_SWITCH_CHANGED

This CL addresses a regression that

  InputMethodManagerService#MSG_HARD_KEYBOARD_SWITCH_CHANGED

uses different data format between the sender and the receiver, which
was introduced in Android L development cycle [1].

This issue becomes observable when and only a hardware keyboard is
attached while the IME switcher dialog is shown hence no one has
noticed it.  However we will soon start relying on that signal to
render the IME switcher button in the IME process at Bug 215551357.
Let's fix this before the bug becomes much more obvious there.

 [1]: I2237ded850a0d4ab43ca441d0b7df13e0958e630
      b64e56aad3ffb267aec44308f57641a4c91caa83

Fix: 215449191
Test: Manually verified with a debugger.
Change-Id: I2dba087f48b37841e7a86ebbd085be0ef72b3f7a