box: expose box_is_orphan method

is_orphan status check is needed by applier in order to tell relay
whether to send the instance's own rows back or not.

Prerequisite #4739

src/box/box.cc

@@ -247,6 +247,12 @@ box_is_ro(void)
 	return is_ro || is_orphan;
 }
 
+bool
+box_is_orphan(void)
+{
+	return is_orphan;
+}
+
 int
 box_wait_ro(bool ro, double timeout)
 {

src/box/box.h

@@ -105,6 +105,9 @@ box_set_ro();
 bool
 box_is_ro(void);
 
+bool
+box_is_orphan(void);
+
 /**
  * Wait until the instance switches to a desired mode.
  * \param ro wait read-only if set or read-write if unset