datasets: initialize after dropping privileges

Move initialization of datasets to a point after privileges
have been dropped.

Ticket 4239

(cherry picked from commit 92eb14c)

src/suricata.c

@@ -2012,8 +2012,6 @@ static int InitSignalHandler(SCInstance *suri)
  * Will be run once per pcap in unix-socket mode */
 void PreRunInit(const int runmode)
 {
-    /* Initialize Datasets to be able to use them with unix socket */
-    DatasetsInit();
     if (runmode == RUNMODE_UNIX_SOCKET)
         return;
 
@@ -2040,6 +2038,7 @@ void PreRunPostPrivsDropInit(const int runmode)
 {
     StatsSetupPostConfigPreOutput();
     RunModeInitializeOutputs();
+    DatasetsInit();
 
     if (runmode == RUNMODE_UNIX_SOCKET) {
         /* As the above did some necessary startup initialization, it