test.py: Make output pretty and show duration

Make the test runner output look pretty and show test duration to make
it visible which tests take the longest time to run.  The output looks
as follows now:

    TEST tst-af-local.so           OK  (3.288 s)
    TEST tst-bdev-write.so         OK  (1.058 s)
    TEST tst-bsd-evh.so            OK  (1.071 s)
    TEST tst-bsd-kthread.so        OK  (1.234 s)
    TEST tst-bsd-taskqueue.so      OK  (1.062 s)
    TEST tst-bsd-tcp1.so           OK  (2.114 s)
    TEST tst-commands.so           OK  (1.141 s)
    TEST tst-condvar.so            OK  (1.776 s)
    TEST tst-dns-resolver.so       OK  (2.560 s)
    TEST tst-epoll.so              OK  (1.952 s)
    TEST tst-except.so             OK  (1.146 s)
    TEST tst-fpu.so                OK  (2.630 s)
    TEST tst-fs-link.so            OK  (1.051 s)
    TEST tst-fs-stress.so          OK  (1.027 s)
    TEST tst-fsx.so                OK  (1.067 s)
    TEST tst-hub.so                OK  (6.256 s)
    TEST tst-huge.so               OK  (2.199 s)
    TEST tst-kill.so               OK  (4.147 s)
    TEST tst-libc-locking.so       OK  (2.110 s)
    TEST tst-loadbalance.so        OK  (1.070 s)
    TEST tst-mmap-file.so          OK  (1.080 s)
    TEST tst-mmap.so               OK  (1.087 s)
    TEST tst-pipe.so               OK  (7.306 s)
    TEST tst-preempt.so            OK  (1.119 s)
    TEST tst-pthread.so            OK  (1.100 s)
    TEST tst-queue-mpsc.so         OK  (3.748 s)
    TEST tst-ramdisk.so            OK  (1.078 s)
    TEST tst-readdir.so            OK  (1.094 s)
    TEST tst-remove.so             OK  (1.030 s)
    TEST tst-rename.so             OK  (1.157 s)
    TEST tst-resolve.so            OK  (1.095 s)
    TEST tst-scheduler.so          OK  (1.087 s)
    TEST tst-sleep.so              OK  (3.083 s)
    TEST tst-solaris-taskq.so      OK  (1.061 s)
    TEST tst-stat.so               OK  (1.106 s)
    TEST tst-strerror_r.so         OK  (1.102 s)
    TEST tst-tcp-sendonly.so       OK  (2.014 s)
    TEST tst-tcp.so                OK  (1.080 s)
    TEST tst-threadcomplete.so     OK  (2.770 s)
    TEST tst-tracepoint.so         OK  (1.109 s)
    TEST tst-truncate.so           OK  (1.083 s)
    TEST tst-utimes.so             OK  (1.079 s)
    TEST tst-vblk.so               OK  (1.310 s)
    TEST tst-vfs.so                OK  (1.118 s)
    TEST tst-yield.so              OK  (1.992 s)
    TEST tst-zfs-mount.so          OK  (1.087 s)
  OK (58 tests run, 82.944 s)

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>