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

...
