[Beignet] compiler_fill_image_1d_array intermittent failure

[Rebecca N. Palmer]

> Both [3.18 kernel] and the 3.16 kernel have a different intermittent failure I have
> yet to investigate:
>
> compiler_fill_image_1d_array()    [FAILED]
>      Error: dst[j*w + i] == 0
>    at file
> /home/rnpalmer/Debian/builds/stackbuild/beignet/utests/compiler_fill_image_1d_array.cpp,
> function compiler_fill_image_1d_array, line 63

The kernel itself (fill j<7,i<32 with 0x03020100) is working correctly; 
the problem is that the initial memset() clear (line 30) sometimes only 
clears half the array (exactly half, i.e. j<4 is filled with 0, but the 
rest is left at whatever it was before).