Fix issue 861: configure.sh fails on mac os x in develop branch https://github.com/OpenBazaar/OpenBazaar/issues/861 

https://github.com/OpenBazaar/OpenBazaar/issues/861 

This updated configure.sh works on macs, both on fresh installs and on upgrades from the last release.

The `servent` was not a typo; in a P2P network each node is a server and a client, hence "servent".