selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock adjustments are in progress

In the past we've warned when ADJ_OFFSET was in progress, usually
caused by ntpd or some other time adjusting daemon running in non
steady sate, which can cause the skew calculations to be
incorrect.

Thus, this patch checks to see if the clock was being adjusted
when we fail so that we don't cause false negatives.

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 <sboyd@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
v2: Widened the checks to look for other clock adjustments that
    could happen, as suggested by Miroslav
v3: Fixed up commit message