BUG/MINOR: task: fix missing include with DEBUG_TASK

Following include reorganzation, there is some missing include files for
task.h when compiling with DEBUG_TASK :
- activity.h for task_profiling_mask
- time.h for now_mono_time()

This is present since the following commit
  d8b325c74826bdb02759f62c41a00455dbae3431
  REORG: task: uninline the loop time measurement code

No need to backport this.
diff --git a/include/haproxy/task.h b/include/haproxy/task.h
index 011ca31..e2c8a99 100644
--- a/include/haproxy/task.h
+++ b/include/haproxy/task.h
@@ -28,6 +28,7 @@
 #include <import/eb32sctree.h>
 #include <import/eb32tree.h>
 
+#include <haproxy/activity.h>
 #include <haproxy/api.h>
 #include <haproxy/fd.h>
 #include <haproxy/global.h>
@@ -37,6 +38,7 @@
 #include <haproxy/task-t.h>
 #include <haproxy/thread.h>
 #include <haproxy/ticks.h>
+#include <haproxy/time.h>
 
 
 /* Principle of the wait queue.