Keeps the served view of the window when focus to the next window

CL[1] intends to reset served view and restart input state when focus to
the next window, which the main idea is try to make the lifecycle of the
input connection can more aligned with the window focus change.

However, this behavior change unexpectedly breaks Gboard
TranslatesUIExtention that will closeExtensionView when
onFinishInputView -> onDeactivate called, while launching language
selection dialog.

Remove the reset logic as the lifecycle of input connection still
needs to break down.

[1]: I8d4fff94ba9313b773bc27fcbd019cc88580d3e9

Fix: 152373385
Test: To make sure not break Bug 148489857 and Bug 148788569, following
auto / manual test to verify:
 - Auto: atest FocusHandlingTest#testKeyboardStateAfterImeFocusableFlagChanged
 - Manual:
    1) Build / install EditTextVariations
    2) Select menu -> Direct-Reply, make sure Notification comes up.
    3) Tap EditText on Notification, verify soft-keyboard is visible.

Change-Id: If20cdb43ecd013c330c5e16c73e9af972bd89f33