install_vme.sh, download mode always enabled

File: https://github.com/aquasecurity/deployments/blob/2022.4/enforcers/vm_enforcer/shell/install_vme.sh

It checks if DOWNLOAD_MODE is 0 bytes, if true enables DOWNLOAD_MODE, it should disable if DOWNLOAD_MODE is 0 bytes.

```
setup_sh_env() {
if [ -z "${INSTALL_PATH}" ]; then
INSTALL_PATH="/opt"
fi
if [ -z "${DOWNLOAD_MODE}" ]; then
DOWNLOAD_MODE=true
fi

...

Open enforcers/vm_enforcer/shell/install_vme.sh and start with setup_sh_env(). Check how DOWNLOAD_MODE behaves when it is set to 0 bytes, then verify that the installer disables download mode in that case while preserving the existing behavior for other values.

Written by the indexing model from the issue text.