tm-threads: add TM_ECODE_DONE state

This patch adds a nex return state which can be used by threads
to warn that a task has been done. In this case, suricata does not
leave.

src/tm-threads-common.h

@@ -85,6 +85,7 @@ typedef enum {
 typedef enum {
     TM_ECODE_OK = 0,    /**< Thread module exits OK*/
     TM_ECODE_FAILED,    /**< Thread module exits due to failure*/
+    TM_ECODE_DONE,    /**< Thread module task is finished*/
 } TmEcode;
 
 /* ThreadVars type */

src/tm-threads.c

@@ -668,6 +668,9 @@ void *TmThreadsSlotPktAcqLoop(void *td) {
             || suricata_ctl_flags) {
             run = 0;
         }
+        if (r == TM_ECODE_DONE) {
+            run = 0;
+        }
     }
     SCPerfSyncCounters(tv, 0);