UiScrollable getChildByText will not scroll lists with floating action buttons

### Description
When using UIScrollable getChildByText on a list view that has a floating action button that appears on scroll, the scroll will stop and return with UiObjectNotFoundException. From watching it looks as though the scroll event gets sent to the button and halts the process.

The easiest place to see it is in the Settings app, going to the Notifications menu and trying to scroll the listview there. If you manually scroll you can see the button that comes up bottom middle which appears to stop it from working.

Also observed in the samsung myFiles app as well if trying to scroll through the files list.

Not a major issue but have to use alternative functions to search lists that have a button come up like that.

androidTestCompile 'com.android.support.test.uiautomator:uiautomator-v18:2.1.3'
Tested on S7 android version 7.0

Start by reproducing the failure in the Android Settings app under Notifications, using UiScrollable.getChildByText on a list with a floating action button; the payload names no source file or test. Trace how the scroll event is handled when the button appears, and consider the issue done when the target can be found without UiObjectNotFoundException in the described cases.

Scritto dal modello di indicizzazione a partire dal testo della issue.