Additional fix for BUG#20294: Instance manager test

im_instance_conf fails randomly.

mysql-test/r/im_options.result

@@ -13,7 +13,10 @@ UNSET mysqld1.server_id;
 ERROR HY000: The instance is active. Stop the instance first
 SET mysqld1.server_id = 11;
 ERROR HY000: The instance is active. Stop the instance first
-CREATE INSTANCE mysqld3 datadir = '/';
+CREATE INSTANCE mysqld3
+datadir = '/',
+server_id = 3,
+socket = "$MYSQL_TMP_DIR/mysqld_3.sock";
 START INSTANCE mysqld3;
 UNSET mysqld3.server_id;
 ERROR HY000: The instance is active. Stop the instance first
@@ -101,12 +104,14 @@ ERROR HY000: Bad instance name. Check that the instance with such a name exists
 --------------------------------------------------------------------
 server_id           = 1
 server_id=2
+server_id=3
 --------------------------------------------------------------------
 UNSET mysqld2.server_id, mysqld3.server_id, mysqld1.ccc;
 ERROR HY000: The instance is active. Stop the instance first
 --------------------------------------------------------------------
 server_id           = 1
 server_id=2
+server_id=3
 --------------------------------------------------------------------
 DROP INSTANCE mysqld3;
 SET mysqld2.server_id=222;

mysql-test/t/im_instance_conf.imtest

@@ -21,6 +21,9 @@
 #   - DROP INSTANCE fails for active instance.
 #   - DROP INSTANCE updates both config file and internal configuration cache;
 #
+# NOTE: each CREATE INSTANCE statement must specify socket-file-name, otherwise
+# this results of the test can be affected by another running test suite.
+#
 ###########################################################################
 
 --source include/im_check_os.inc

mysql-test/t/im_options.imtest

@@ -21,12 +21,15 @@
 #   - server_id
 #   - port
 #   - nonguarded
-
+#
 # Let's test SET statement on the option 'server_id'. It's expected that
 # originally the instances have the following server ids and states:
 #  - mysqld1: server_id: 1; running (online)
 #  - mysqld2: server_id: 2; stopped (offline)
 #
+# NOTE: each CREATE INSTANCE statement must specify socket-file-name, otherwise
+# this results of the test can be affected by another running test suite.
+#
 ###########################################################################
 
 --source include/im_check_os.inc
@@ -76,7 +79,10 @@ SET mysqld1.server_id = 11;
 #   - start it;
 #   - try to set/unset options;
 
-CREATE INSTANCE mysqld3 datadir = '/';
+CREATE INSTANCE mysqld3
+  datadir = '/',
+  server_id = 3,
+  socket = "$MYSQL_TMP_DIR/mysqld_3.sock";
 START INSTANCE mysqld3;
 
 # FIXME: START INSTANCE should be synchronous.