Inconsistency in location of secret keys for mqtt-gdp-gateway
gdp/gdp_crypto.c the search path for reading secret keys is:
"." ":KEYS" ":~/.swarm/gdp/keys" ":/usr/local/etc/swarm/gdp/keys" ":/etc/swarm/gdp/keys"
However, the startup scripts for mqtt-gdp-gateway install new keys in
/etc/gdp/keys. This inconsistency should be fixed. Note that newer versions of the mqtt-gdp-gateway startup script explicitly name the keys directory, so this bug doesn't exhibit itself; nonetheless it should still be fixed.