thread pool: mark epicsJobCreate() as safe for job functions

Also, use epicsJobMove() to avoid some redundant code

src/libCom/pool/epicsThreadPool.h

@@ -100,6 +100,7 @@ epicsShareExtern void* _epicsJobArgSelf;
 /* creates, but does not add, a new job.
  * If pool in NULL then the job is not associated with any pool and
  * epicsJobMove() must be called before epicsJobQueue()
+ * Safe to call from a running job function.
  * returns a new job pointer, or NULL on error
  */
 epicsShareFunc epicsJob* epicsJobCreate(epicsThreadPool* pool,

src/libCom/pool/poolJob.c

@@ -152,17 +152,11 @@ epicsJob* epicsJobCreate(epicsThreadPool* pool,
     if(arg==&_epicsJobArgSelf)
         arg=job;
 
-    job->pool=pool;
+    job->pool=NULL;
     job->func=func;
     job->arg=arg;
 
-    if(pool) {
-        epicsMutexMustLock(pool->guard);
-
-        ellAdd(&pool->owned, &job->jobnode);
-
-        epicsMutexUnlock(pool->guard);
-    }
+    epicsJobMove(job, pool);
 
     return job;
 }