Another cut at trying to get mqtt-gdp-gateway running under Docker.
Change GDP_INSTALL_ROOT to GDP_ROOT, since all of the scripts in
$gdp/adm are looking for that name. An even better choice would be
GDP_RUN_ROOT, but we'll survive.
Rationalize macro names to avoid confusion and for consistency with the
base GDP code:
* GDP_ROOT => GDP_INSTALL_ROOT
* GDPROOT => GDP_SRC_ROOT
* GDPADM => GDP_ADM
Adjust mqtt-gdp-gateway restart interval to be less aggressive.
Tweak systemd service files so that there will be a brief pause before
starting mqtt-gdp-gateway on reboot to let the network settle.
Clean up mqtt-gdp-gateway installation scripts and startup.
Tweaks for mqtt-gdp-gateway systemd service files to try to ensure that
the network is up before the gateway is started.
systemd service files are very picky about command lines.
Extensive rework on mqtt-gdp-gateway startup scripts. Not yet complete.