`$SSHPATH` is not used in the function to check if binaries are available

[JayGoldberg]

for cmd in ssh nc; do
    if [ ! $(which $cmd) ]; then
      ErrMsg "[FATAL] Can't find $cmd, make sure the required binaries \
      are installed and that their paths in the config are correct"
      exit 1
    fi
  done

In this code we do not take into account the rstunnel.conf overrides for binary locations, instead relying on $PATH.