Hide keyboard after backup passphrase entered

Fixes #7508

res/layout/enter_backup_passphrase_dialog.xml

@@ -8,13 +8,13 @@
             android:layout_width="match_parent"
             android:layout_height="wrap_content">
 
-        <AutoCompleteTextView
+        <android.support.design.widget.TextInputEditText
                 android:id="@+id/restore_passphrase_input"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:hint="@string/enter_backup_passphrase_dialog__backup_passphrase"
                 android:imeOptions="actionDone"
-                android:inputType="textVisiblePassword" />
+                android:inputType="number" />
 
     </android.support.design.widget.TextInputLayout>
 </FrameLayout>

src/org/thoughtcrime/securesms/RegistrationActivity.java

@@ -30,6 +30,7 @@ import android.view.LayoutInflater;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.animation.OvershootInterpolator;
+import android.view.inputmethod.InputMethodManager;
 import android.widget.ArrayAdapter;
 import android.widget.EditText;
 import android.widget.Spinner;
@@ -354,6 +355,9 @@ public class RegistrationActivity extends BaseActionBarActivity implements Verif
         .setTitle(R.string.RegistrationActivity_enter_backup_passphrase)
         .setView(view)
         .setPositiveButton(getString(R.string.RegistrationActivity_restore), (dialog, which) -> {
+          InputMethodManager inputMethodManager = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
+          inputMethodManager.hideSoftInputFromWindow(prompt.getWindowToken(), 0);
+
           restoreButton.setIndeterminateProgressMode(true);
           restoreButton.setProgress(50);