Test for setting general_log_file to a directory fails

since /tmp is used as the directory. It does not always
exist so let's use one that always exists MYSQLTEST_VARDIR

mysql-test/r/log_state.result

@@ -94,8 +94,8 @@ Variable_name	Value
 log_output	FILE,TABLE
 set global general_log_file='/not exiting path/log.master';
 ERROR 42000: Variable 'general_log_file' can't be set to the value of '/not exiting path/log.master'
-set global general_log_file='/tmp';
-ERROR 42000: Variable 'general_log_file' can't be set to the value of '/tmp'
+set global general_log_file='MYSQLTEST_VARDIR';
+ERROR 42000: Variable 'general_log_file' can't be set to the value of 'MYSQLTEST_VARDIR'
 set global general_log_file='';
 ERROR 42000: Variable 'general_log_file' can't be set to the value of ''
 show variables like 'general_log_file';

mysql-test/t/log_state.test

@@ -70,12 +70,19 @@ show variables like 'general_log_file';
 show variables like 'slow_query_log_file';
 show variables like 'log_output';
 
+# Can't set general_log_file to a non existing file
 --error 1231
 set global general_log_file='/not exiting path/log.master';
+
+# Can't set general_log_file to a directory
+--replace_result $MYSQLTEST_VARDIR MYSQLTEST_VARDIR
 --error 1231
-set global general_log_file='/tmp';
+eval set global general_log_file='$MYSQLTEST_VARDIR';
+
+# Can't set general_log_file to empty string
 --error 1231
 set global general_log_file='';
+
 --replace_column 2 #
 show variables like 'general_log_file';
 set global general_log= OFF;