m4v_h263_enc_test: Fix leaks in error cases

These leaks aren't really consequential since this is a standalone
test.  But by putting in simple fixes for these, we reduce the
noise when using static analysis to find leaks in Android code.

Test: TreeHugger

Change-Id: Iace7028f8bc3951abf72ddcec2b741b7a5f61a3e