testing: Reduce testing runtime by reusing SSH sessions.

By using the ControlMaster and ControlPath options, existing SSH sessions
are reused (a session to each host is opened at the beginning of a test
run).  Also, RC4 is used as encryption algorithm to further improve the
performance.  These changes reduce the runtime by over 20%.

testing/scripts/restore-defaults

@@ -46,6 +46,6 @@ then
     for host in `ls $TESTSDIR/${testname}/hosts`
     do
 	eval HOSTLOGIN="root@`echo $HOSTNAMEIPV4 | sed -n -e "s/^.*${host},//gp" | awk -F, '{ print $1 }' | awk '{ print $1 }'`"
-	scp -r $HOSTCONFIGDIR/${host}/etc $HOSTLOGIN:/ > /dev/null 2>&1
+	scp $SSHCONF -r $HOSTCONFIGDIR/${host}/etc $HOSTLOGIN:/ > /dev/null 2>&1
     done
 fi