kselftests: timers: leap-a-day: Change default arguments to help test runs

Change default arguments for leap-a-day to always set the time
each iteration (rather then waiting for midnight UTC), and to
only run 10 interations (rather then infinite).

If one wants to wait for midnight UTC, they can use the new -w
flag, and we add a note to the argument help that -i -1 will
run infinitely.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: stable <stable@vger.kernel.org> [4.13+]
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>