jtag: fix clang ulink memory leaks

Memory leaks discovered by clang 3.1

Change-Id: I8a784ba9726deac508424eddb27e9c8409e2773f
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/795


Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>