Fix uninitialized index array

Fix uninitialized index array

The test is doing a glDrawRangeElements using uninitialized data for
the element array. ANGLE validates that the indices fall within the
specified range. Data needs to be initialized to ensure that happens.

The spec says:
It is an error for index values (other than the primitive restart index,
when primitive restart is enabled) to lie outside the range [start, end], but
implementations are not required to check for this. Such indices will cause
implementation-dependent behavior.

Either the test needs to allow for an error or initialize the data so
as to be valid for the call.

Affected Test:
    dEQP-GLES31.functional.debug.negative_coverage.get_error.vertex_array.draw_range_elements

Components: OpenGL ES
VK-GL-CTS issue: 2118

Change-Id: I51f8abb86f088b67990001454bb00d59313200c2
(cherry picked from commit bf7a86af5a959c3f4ad39deabe8b396d8581470a)