Set config_file_path in storage::node.

This change makes it so that storage::node sets config_file_path
for each of the services correctly. Previously this would cause
swift config file fragments to get written to
/etc/swift/<service>/600?.conf instead of /etc/swift/<service>.conf.

Fixes config issues for me on Fedora when using swift::storage::node.

Change-Id: I8d0ce87a545af805e24c5594b437483f9b479c9d