Split disk creation out of configure_swift()

Grenade needs to be able to configure Swift without initializing the
backing disk files.  Move it into create_swift_disk() and call
from init_swift().

Also move start of n-obj (if swift3 is not enabled) to start_nova().

Change-Id: Id33939182d84eeff10ba4139eeced2c1bc532f0f
diff --git a/lib/nova b/lib/nova
index 4449f81..8f74897 100644
--- a/lib/nova
+++ b/lib/nova
@@ -660,6 +660,11 @@
     screen_it n-xvnc "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-xvpvncproxy --config-file $NOVA_CONF"
     screen_it n-spice "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-spicehtml5proxy --config-file $NOVA_CONF --web $SPICE_DIR"
     screen_it n-cauth "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-consoleauth"
+
+    # Starting the nova-objectstore only if swift3 service is not enabled.
+    # Swift will act as s3 objectstore.
+    is_service_enabled swift3 || \
+        screen_it n-obj "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-objectstore"
 }
 
 # stop_nova() - Stop running processes (non-screen)