[Android] Fix white screen issue after press home button

Call onHide() when activity stopped, and onShow() when activity started,
instead of activity resumed and paused.
activity::onStop() means activity is hidden, and activity::onPause() means
activity partially visible.

BUG=XWALK-2188
Merge pull request #2246 from kurli/int_onshow_onhide

[Android] Fix white screen issue after press home button