A deployer may want to remove a Swift node from a load balancer for
maintenance or upgrade. This patch provides an optional mechanism for
this. The healthcheck filter config can specify "disable_path" which is
a filesystem path. If a file is present at that location, the
healthcheck middleware returns a 503 with a body of "DISABLED BY FILE".
So a deployer can configure "disable_path" and then touch that
filesystem path, wait for the proxy to be removed from the load balancer
pool, perform maintenance/upgrade, and then remove the "disable_path"
file.
Also cleaned up the conf file man pages a bit.
Change-Id: I1759c78c74910a54c720f298d4d8e6fa57a4dab4
b8e3e9e1c2