Bug#26622 MASTER_POS_WAIT does not work as documented

MASTER_POS_WAIT return values are different than expected when the server is not a slave. 
It returns -1 instead of NULL.

Fixed with correcting  st_relay_log_info::wait_for_pos() to return the proper
value in the case of rli info is not inited.

mysql-test/r/rpl_master_pos_wait.result

@@ -16,3 +16,9 @@ select master_pos_wait('master-bin.999999',0);
 stop slave sql_thread;
 master_pos_wait('master-bin.999999',0)
 NULL
+"*** must be empty ***"
+show slave status;
+"*** must be NULL ***"
+select master_pos_wait('foo', 98);
+master_pos_wait('foo', 98)
+NULL

mysql-test/t/rpl_master_pos_wait.test

@@ -15,4 +15,15 @@ stop slave sql_thread;
 connection slave;
 reap;
 
+#
+# bug#26622 MASTER_POS_WAIT does not work as documented
+#
+
+connection master;
+echo "*** must be empty ***";
+query_vertical show slave status;
+
+echo "*** must be NULL ***";
+select master_pos_wait('foo', 98);
+
 # End of 4.1 tests

sql/slave.cc

@@ -2685,7 +2685,7 @@ int st_relay_log_info::wait_for_pos(THD* thd, String* log_name,
                                     longlong timeout)
 {
   if (!inited)
-    return -1;
+    return -2;
   int event_count = 0;
   ulong init_abort_pos_wait;
   int error=0;