Set 067-preemptive-unpark success flag sooner

Empirically, the println occasionally takes more than 3 seconds
on host, causing the flag to get set too late if we do so after
the println.

Remove clearStack(), which I can't believe still had any effect.
It just wrote to dead locals.

Bug: 22242462
Test: .../testrunner.py --host -b 067-preemptive-unpark
Change-Id: I1424396e73d2546c74ea9cd82ecf2cdb59734b32
1 file changed