jtag/tcl: fix a double free of jim object

jtag/tcl: fix a double free of jim object

The Jim_SetResultFormatted() frees jim object earlier and the
Jim_FreeNewObj() does it second time. It breaks the memory heap.

To avoid it the Jim_IncrRefCount() + Jim_DecrRefCount() should be used
instead of the Jim_FreeNewObj() call.

Change-Id: Ifa5f38009b2d617624b5f27e916720888a3dbad9
Signed-off-by: Mikhail Rasputin <mikhail.godlike.rasputin@yandex.ru>
Reviewed-on: http://openocd.zylin.com/5724
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>