glimagesink: set last sample disabled if input is "external-oes"
The last sample causes error log of: gstglmemory.c:926:_gl_tex_copy: Cannot copy External OES textures
So we should disable last sample if the input is "external-oes".
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The last sample causes error log of: gstglmemory.c:926:_gl_tex_copy: Cannot copy External OES textures
So we should disable last sample if the input is "external-oes".