adjust timeout value in main.ssl_timeout test

fixes sporadic failures under --valgrind

mysql-test/main/ssl_timeout.result

 # connect with read timeout so SLEEP() should timeout
-connect  ssl_con,localhost,root,,,,,SSL read_timeout=5;
+connect  ssl_con,localhost,root,,,,,SSL read_timeout=5$_timeout_adjustment;
 # Check ssl turned on
 SELECT (VARIABLE_VALUE <> '') AS have_ssl FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME='Ssl_cipher';
 have_ssl

mysql-test/main/ssl_timeout.test

 --source include/have_ssl_communication.inc
+--source include/slow_environ.inc
 
 # Save the initial number of concurrent sessions
 --source include/count_sessions.inc
 
 --echo # connect with read timeout so SLEEP() should timeout
-connect (ssl_con,localhost,root,,,,,SSL read_timeout=5);
+connect (ssl_con,localhost,root,,,,,SSL read_timeout=5$_timeout_adjustment);
 
 --echo # Check ssl turned on
 SELECT (VARIABLE_VALUE <> '') AS have_ssl FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME='Ssl_cipher';