Use clock_boottime_or_monotonic() everywhere to pick clocksrc.

This clocksrc is used every measurement and should be used
everywhere, not just in one location.

Author: ahkok

src/store.c

@@ -53,7 +53,7 @@ static int skip = 0;
 double gettime_ns(void) {
         struct timespec n;
 
-        clock_gettime(CLOCK_MONOTONIC, &n);
+        clock_gettime(clock_boottime_or_monotonic(), &n);
 
         return (n.tv_sec + (n.tv_nsec / (double) NSEC_PER_SEC));
 }