Fix for BUG#20716: SHOW INSTANCES statement causes races in IM tests.

Fix for the bug in mysql-test-run.pl which prevents other tests succeed
after IM-test failure.
  
The idea of the fix of BUG#20716 is to:
  1. Check each SHOW INSTANCES statement, add necessary "sleep" instruction before;
  2. Move all environment checkings into the one file and include it everywhere.


mysql-test/mysql-test-run.pl:
  Fix bug in mysql-test-run.pl -- kill leftovers if some
  guarded mysqld-instance is still alive after IM shutdown.
mysql-test/r/im_daemon_life_cycle.result:
  Updated result file.
mysql-test/r/im_life_cycle.result:
  Updated result file.
mysql-test/r/im_options_set.result:
  Updated result file.
mysql-test/r/im_options_unset.result:
  Updated result file.
mysql-test/r/im_utils.result:
  Updated result file.
mysql-test/t/im_daemon_life_cycle.imtest:
  Include im_check_env.inc for the checking of environment.
mysql-test/t/im_life_cycle.imtest:
  Include im_check_env.inc for the checking of environment.
mysql-test/t/im_options_set.imtest:
  Include im_check_env.inc for the checking of environment.
mysql-test/t/im_options_unset.imtest:
  Include im_check_env.inc for the checking of environment.
mysql-test/t/im_utils.imtest:
  Include im_check_env.inc for the checking of environment.
mysql-test/include/im_check_env.inc:
  A new file to be included in each IM-test.
  The statements in the file ensure that starting
  conditions (environment) are as expected.

mysql-test/r/im_utils.result

@@ -1,4 +1,7 @@
 Success: the process has been started.
+SHOW VARIABLES LIKE 'server_id';
+Variable_name	Value
+server_id	1
 SHOW INSTANCES;
 instance_name	status
 mysqld1	online