BUG#37975: wait_for_slave_* should increase the timeout

Post-push fixes: I forgot to include the new files
start_slave.inc and stop_slave.inc in the previuos push.


mysql-test/include/start_slave.inc:
  Added file.
  Purpose: start slave synchronously, waiting for the two
  threads to start.
mysql-test/include/stop_slave.inc:
  Added file.
  Purpose: stop slave synchronously, waiting for the two
  threads to stop.

mysql-test/include/start_slave.inc

+# ==== Purpose ====
+#
+# Issues START SLAVE on the current connection. Then waits until both
+# the IO and SQL threads have started, or until a timeout is reached.
+#
+# Please use this instead of 'START SLAVE', to reduce the risk of test
+# case bugs.
+#
+# ==== Usage ====
+#
+# source include/wait_for_slave_to_start.inc;
+#
+# Parameters to this macro are $slave_timeout and
+# $slave_keep_connection. See wait_for_slave_param.inc for
+# descriptions.
+
+--disable_query_log
+START SLAVE;
+--enable_query_log
+--echo include/start_slave.inc
+source include/wait_for_slave_to_start.inc;

mysql-test/include/stop_slave.inc

+# ==== Purpose ====
+#
+# Issues STOP SLAVE on the current connection. Then waits until both
+# the IO and SQL threads have stopped, or until a timeout is reached.
+#
+# Please use this instead of 'STOP SLAVE', to reduce the risk of test
+# case bugs.
+#
+# ==== Usage ====
+#
+# source include/wait_for_slave_to_start.inc;
+#
+# Parameters to this macro are $slave_timeout and
+# $slave_keep_connection. See wait_for_slave_param.inc for
+# descriptions.
+
+--disable_query_log
+STOP SLAVE;
+--enable_query_log
+--echo include/stop_slave.inc
+source include/wait_for_slave_to_stop.inc;