Bhv 11099 Has improper position for disabled control.

Issue
------
If tooltip is showing over disabled control, it could not calculate its position

Cause
-------
Current position calculation of tooltip is based on `enyo.Spotlight.getCurrent()`
However disabled control could not have spotlight focus. It makes problem.

Fix
-----
From `onenter` event occur, it preserves event sender and delivers it to `moon.tooltip`.
If `enyo.Spotlight.getCurrent()` is not existed, `adjustPosition()` will use preserved event sender

Enyo-DCO-1.1-Signed-off-by: David Um david.um@lge.com
Hi @aarontam, It is very interesting.
What I told you prev comment, there are some weird behavior.
Focus disabled button -> tooltip showing up
Focus enabled button -> tooltip showing up
Focus disabled button again -> tooltip does not showing up

But its issue is not related with tooltip. 
If we use 'small = true' for moon.Button, this issue is not reproduced.

I think we'd better resolve it in different jira ticket