Fix swift.conf custom configuration path collision

Both swift.conf and proxy-server.conf are affected be
/etc/kolla/config/swift/proxy-server.conf. However, some options in
proxy-server.conf are not valid in swift.conf.

This change keeps this path for proxy-server.conf, but modifies the path
for swift.conf to /etc/kolla/config/swift/proxy-server/swift.conf. The
same applies for other services, object-*, account-*, container-*.

Change-Id: I600891a15244ce705861f6ec93eec1d5ba83c1b8
Closes-Bug: #1849265