su/su01_s1: fix mismatched double quotation marks

Expect code
* spawn su -c "/bin/su root -c \"echo \"\\\$TEST_LINE > $TEST_ENV_FILE\"\""
will be translated to
* spawn su -c /bin/su root -c "echo "\$TEST_LINE > /tmp/TEST_ENV_FILE_ROOT""
which actually should be
* spawn su -c /bin/su root -c "echo \$TEST_LINE > /tmp/TEST_ENV_FILE_ROOT"

Signed-off-by: DAN LI <li.dan@cn.fujitsu.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>