Remove timer in favor of sdeventplus/utility/timer

This removes the custom timer implementation and moves to the
sdeventplus utility. Functionally this should make no change

Tested:
    Built and run through the unit test suite.

Change-Id: Ib7ee90d489d5db72496aaaca91c3cf5490ad47d6
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/monitor/tach_sensor.cpp b/monitor/tach_sensor.cpp
index 26ba3c9..5494450 100644
--- a/monitor/tach_sensor.cpp
+++ b/monitor/tach_sensor.cpp
@@ -221,24 +221,11 @@
 
 void TachSensor::startTimer(TimerMode mode)
 {
-    if (!timerRunning())
+    if (!timerRunning() || mode != _timerMode)
     {
-        _timer.start(
-                getDelay(mode),
-                util::Timer::TimerType::oneshot);
+        _timer.restartOnce(getDelay(mode));
         _timerMode = mode;
     }
-    else
-    {
-        if (mode != _timerMode)
-        {
-            _timer.stop();
-            _timer.start(
-                    getDelay(mode),
-                    util::Timer::TimerType::oneshot);
-            _timerMode = mode;
-        }
-    }
 }
 
 std::chrono::microseconds TachSensor::getDelay(TimerMode mode)