Fix stencil buffer bug.

Stencil test is enabled by setStencilFromClip(), but not disabled
in some use case, which causes some of the pixels are discarded by
mistake in draws followed. Disable stencil test when there is no
dirty clip.

CRs-Fixed: 539456

Change-Id: I318fb47212e49e2da89bcbfd161a1689ef91b02f