In the case where:
* global-motion and ext-inter are both enabled
* cb4x4 is disabled
* We have an 8x8 macroblock which is partitioned into smaller blocks

the function is_nontrans_global_motion has a bug where it will
always act as if that macroblock does not use global motion. This
patch fixes that logic bug.

Change-Id: I712d7bab6d646726d97aa37630399b4bcbee7757