Print nanoseconds too on log timestamps

If we're being extra-verbose, we'll have multiple log lines per second
so we need more help to sort things properly.

Change-Id: I651a83250673d76372f89a2a7b8567f656de81e3
diff --git a/test/test-common b/test/test-common
index 7b59328..0510678 100755
--- a/test/test-common
+++ b/test/test-common
@@ -33,7 +33,7 @@
 # Function for output; write text to terminal and to our logfile, with
 # timestamp for sorting.
 log () {
-    DATE=$(date -u +%F/%H:%M:%S)
+    DATE=$(date -u +%F/%H:%M:%S.%N)
     if [ "${LOGFILE}"x = ""x ] ; then
 	LOGFILE=$0.log
     fi