Decrease logging severity for common message

The health monitor always logs this for each metric on start-up until
enough samples have been collected.  Decrease it to debug log level.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4b321b02c88c9e4b8d0b557e711a1c4fa41b1e44
diff --git a/health_metric.cpp b/health_metric.cpp
index abe77af..a160025 100644
--- a/health_metric.cpp
+++ b/health_metric.cpp
@@ -210,7 +210,7 @@
     if (history.size() < config.windowSize)
     {
         // Wait for the metric to have enough samples to calculate average
-        info("Not enough samples to calculate average");
+        debug("Not enough samples to calculate average");
         return;
     }