Allow SOCKS proxy configuration for Presto coordinator

[swaranga]

Currently there doesn't seem to be any way in which I can specify a SOCKS proxy to be applied in the Http client while attempting to connect to the presto co-ordinator. SOCKS proxy would be helpful when Airpal is installed in a different host than the Presto installation and would need a SOCKS proxy to conect to Presto (example presto installation in AWS EMR and Airpal installation is a different non-EMR host).