BUG/MINOR: debug: don't check the call date on tasklets

tasklets don't have a call date, so when a tasklet is cast into a task
and is present at the end of a page we run a risk of dereferencing
unmapped memory when dumping them in ha_task_dump(). This commit
simplifies the test and uses to distinct calls for tasklets and tasks.
No backport is needed.
diff --git a/src/debug.c b/src/debug.c
index a7c3b3a..2829851 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -84,12 +84,18 @@
 		return;
 	}
 
-	chunk_appendf(buf,
-	              "%p (%s) calls=%u last=%llu%s\n",
-	              task, TASK_IS_TASKLET(task) ? "tasklet" : "task",
-	              task->calls,
-	              task->call_date ? (unsigned long long)(now_mono_time() - task->call_date) : 0,
-	              task->call_date ? " ns ago" : "");
+	if (TASK_IS_TASKLET(task))
+		chunk_appendf(buf,
+		              "%p (tasklet) calls=%u\n",
+		              task,
+		              task->calls);
+	else
+		chunk_appendf(buf,
+		              "%p (task) calls=%u last=%llu%s\n",
+		              task,
+		              task->calls,
+		              task->call_date ? (unsigned long long)(now_mono_time() - task->call_date) : 0,
+		              task->call_date ? " ns ago" : "");
 
 	chunk_appendf(buf, "%s"
 	              "  fct=%p (%s) ctx=%p\n",