Fixed extraScrollHeight bug with ScrollView

[ana-neto]

I came across a bug on this library related with setting an extraScrollHeight on the KeyboardAwareView. This changes fix the extra margin that appears after the keyboard disappears on the ScrollView. What would happen is:

• I clicked on an input and the keyboard showed
• The View would scroll up to acomodate the extraScrollHeight I defined through props
• When I clicked outside the input, the keyboard closed
• An extra margin the same height as extraScrollHeight would appear on the View

This was caused because on _resetKeyboardSpace you were setting
keyboardSpace: number = this.props.viewIsInsideTabBar ? _KAM_DEFAULT_TAB_BAR_HEIGHT + this.props.extraScrollHeight || 0 : this.props.extraScrollHeight || 0

which caused the keyboardSpace to be extraScrollHeight instead of 0 after the keyboard closed.

Hope this helps!