Enable swift by default.

- Set by default SWIFT_REPLICAS to 1 since this is the most common use
  case when using it in devstack.
- If we have swift_replicas to 1 launch the object container account and
  proxy servers in foreground in screen.
- Allow any s- services if we have just 'swift' in service enabled
  instead of having to specify all s- services to enable swift. This will be
  removed in the future.
- Set object server starting at 6013 instead of 6010 to not conflict
  with remote ssh x11 forwarding.

Change-Id: I890b6953b70283bfa0927fff0cf5e92f3c08455b
diff --git a/exercises/swift.sh b/exercises/swift.sh
index 46ac2c5..c4ec3e9 100755
--- a/exercises/swift.sh
+++ b/exercises/swift.sh
@@ -35,7 +35,7 @@
 
 # If swift is not enabled we exit with exitcode 55 which mean
 # exercise is skipped.
-is_service_enabled swift || exit 55
+is_service_enabled s-proxy || exit 55
 
 # Container name
 CONTAINER=ex-swift