Blender Git Loki

NLA: Fix Strip Truncate When Next to Transition

**Problem**:
Translating a strip will truncate it when next to a transition.

**Solution**:
The code only accounted for the prev/next strip for whether it exceeds.
When it was a transition, the exceed logic fails. Now, we use the
nearest non-transition strip instead.

Reviewed By: sybren, #animation_rigging

Differential Revision: https://developer.blender.org/D10083