Drop log.h include from helpers.h

With the relocation of several functions, including inline functions,
from helpers to util, we no longer need to include log.h.  Which is a
good thing, since any subsystem that needs logging should explicitly
include log.h

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

plugins/rtc.c

@@ -35,6 +35,7 @@
 #include "finit.h"
 #include "helpers.h"
 #include "plugin.h"
+#include "log.h"
 
 /*
  * Kernel RTC driver validates against this date for sanity check.  The