locks: Use in-house pid_in_pstree helper

This code is for older kernels that don't have locks info
in fdinfo files. So don't keep global pstree helper for this.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/include/pstree.h

@@ -84,7 +84,6 @@ struct pstree_item *pstree_item_by_real(pid_t virt);
 struct pstree_item *pstree_item_by_virt(pid_t virt);
 
 extern int pid_to_virt(pid_t pid);
-extern bool pid_in_pstree(pid_t pid);
 
 struct task_entries;
 extern struct task_entries *task_entries;

criu/proc_parse.c

@@ -1932,6 +1932,11 @@ static int parse_file_lock_buf(char *buf, struct file_lock *fl,
 	return 0;
 }
 
+static bool pid_in_pstree(pid_t pid)
+{
+	return pstree_item_by_real(pid) != NULL;
+}
+
 int parse_file_locks(void)
 {
 	struct file_lock *fl;

criu/pstree.c

@@ -959,8 +959,3 @@ int pid_to_virt(pid_t real)
 		return item->pid.virt;
 	return 0;
 }
-
-bool pid_in_pstree(pid_t pid)
-{
-	return pstree_item_by_real(pid) != NULL;
-}