sys_util: timerfd: Add ability to check if the timer is armed
sys_util: timerfd: Add ability to check if the timer is armed

This allows users to only arm timers if not already armed.

Signed-off-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Change-Id: I8d7c6a7643a2ae2ce4b5679107bfd2be6e4adf3a
Reviewed-on: https://chromium-review.googlesource.com/1214442
Reviewed-by: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm