make the bind_port config setting required

In a long-term effort to change the recommended ports for Swift,
the first step is to require the bind_port in config files. Later,
we can change the recommended setting.

Anyone currently explicitly setting the ports will not be affected.
Anyone not setting the ports will need to specify them to match their
rings.

DocImpact

Change-Id: Icca83a263acdd0afc9016424a3e9f8c15e944789
Merge "make the bind_port config setting required"