strace: increase ptest timeout duration 120->240s

solve qual_fault-syscall.test and qual_fault.test
failing due to timeout.

Bug 14165

Signed-off-by: Yi Fan Yu <yifan.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 5af9f32d)
Signed-off-by: Steve Sakoman <steve@sakoman.com>