[MaterialTimePicker] Keyboard re-appears after closing dialog

Nobody has claimed this yet.

**Description:**
Using the MaterialTimePicker dialog with _INPUT_MODE_KEYBOARD_ and pressing either positive or negative button will cause the keyboard to re-appear (but alphanumeric, not with digits).

This does not occur when dismissing the dialog by clicking outside of it, only when pressing Cancel or OK while the digits keyboard is open.

https://user-images.githubusercontent.com/11249107/103244036-5fef2f00-4964-11eb-8450-419db5ee3ed1.mp4

Maybe the following is related:
```
2020-12-28 23:17:48.041 1291-1291/com.google.android.inputmethod.latin E/KeyboardViewController: KeyboardViewController.show():438 Requesting to show sub view with id 2131428318(key_pos_password_header_numbers) which doesn't exist in current keyboard view
jyl
at klb.a(PG:195)
at bty.a(PG:4)
at com.google.android.apps.inputmethod.latin.keyboard.LatinPasswordKeyboard.a(PG:19)
at kfh.a(PG:15)
at kev.a(PG:31)
at kev.H(PG:26)
at kez.d(PG:10)
at kez.b(PG:108)
at com.android.inputmethod.latin.LatinIME.b(PG:339)
at dwq.onStartInputView(PG:786)
at android.inputmethodservice.InputMethodService.doStartInput(InputMethodService.java:2339)
at android.inputmethodservice.InputMethodService$InputMethodImpl.startInput(InputMethodService.java:620)
at android.inputmethodservice.InputMethodService$InputMethodImpl.dispatchStartInputWithToken(InputMethodService.java:649)
at android.inputmethodservice.IInputMethodWrapper.executeMessage(IInputMethodWrapper.java:199)
at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:44)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
```

**Expected behavior:** The keyboard does not re-open after closing the dialog.

**Source code:**
```
val dialog = MaterialTimePicker.Builder()
.setHour(time.hour)
.setMinute(time.minute)
.setTimeFormat(if (is24HourFormat) TimeFormat.CLOCK_24H else TimeFormat.CLOCK_12H)
.setInputMode(INPUT_MODE_KEYBOARD)
.build()
dialog.show(parentFragmentManager, "MaterialTimePicker")
```

**Android API version:** 26 and 30

**Material Library version:** 1.3.0-alpha03

**Device:** Emulator Nexus 4 API 30 and Samsung SM-A320FL API level 26

Start by reproducing the issue with MaterialTimePicker in INPUT_MODE_KEYBOARD on the reported Android API levels, testing both positive and negative buttons versus outside dismissal. Trace the dialog's keyboard and focus handling; done means closing with OK or Cancel does not reopen an alphanumeric keyboard.

Written by the indexing model from the issue text.