Allow apps to hide the soft keyboard even in a transient state.

Since I69b88989ae4d0fe056e9ab8d67d0a955dd10e6d9, we have
asserted that the following test cases can pass with CTS.

    assertTrue(imm.showSoftInput(
            view, InputMethodManager.SHOW_IMPLICIT));
    assertTrue(imm.hideSoftInputFromWindow(token, 0));

This CL fixes the test failure caused by
I33dc6278fd892f26e56352722bf9449b8b102030 in the above
CTS case.

Note that the test failure occurs only when the application
tries to close the software keyboard during IMMS#mInputShown
and IMMS#mImeWindowVis are in a transiently inconsistent
state.

Bug: 21727232
Change-Id: I195a9f9644583cb1172f48801e87273ad8def850