Fixed escaping of the special characters in the environment variables

When I create simple script

```sh
cat > testenv.sh <<EOF
#!/bin/sh
echo $TESTENV
EOF
```

and submit batch job with torque-4.2.4.2 qsub command

```sh
TESTENV="first,second" qsub -q queue@torque -v TESTENV testenv.sh
```

than I'm getting only "first" in job standard output. I think this behavior is caused by missing copy_env_value function. This function escapes special characters that comes from environment variables (copy_env_value was used in the past, e.g. in torque 2.5.x qsub sources).