Remove padding from call buttons to fix undesired cropping.

Padding was added to the sides of the call button row in order to
prevent false touches. However, this additional padding causes cropping
of the background on the two buttons on the far left and far right when
all 5 buttons are present on low resolution devices. Since on high
resolution devices there is more than enough extra space on the left and
right, this padding is being removed to eliminate cropping.

Bug: 18122087
Change-Id: Ie948d9cbe4ef7025702ae1f4666354ab1be76bbc