Fix various things when n-cell is enabled

1) Use the newer cell_type configuration option instead of overriding
the compute_api_class.

2) A nova-cells service is started for both the API cell (region) and
the compute cell (child).  The screen names were both 'n-cell' which
caused both services to log to the same log file.  The screen names have
been changed to n-cell-region and n-cell-child.

3) Security groups are not supported with cells.  Multiple exercises are
patched to use the 'default' security group instead of creating a new
one.  Additionally, if one uses the 'default' security group, do not try
to delete it, as one can never delete the default.

4) Disable the floating_ips and aggregates exercises when n-cell is
enabled, as they are not supported by cells.

5) Related to #4, disable the floating_ips tests within euca.sh

6) Update the README.md.  No services need to be disabled, and one only
needs to enable the n-cell service.

Change-Id: I9782d1e3cda3c9dd3daefa15c043f5b06473cb87
diff --git a/lib/nova b/lib/nova
index 617fb08..7a5ff1f 100644
--- a/lib/nova
+++ b/lib/nova
@@ -568,11 +568,11 @@
         iniset $NOVA_CELLS_CONF DEFAULT rabbit_virtual_host child_cell
         iniset $NOVA_CELLS_CONF DEFAULT dhcpbridge_flagfile $NOVA_CELLS_CONF
         iniset $NOVA_CELLS_CONF cells enable True
+        iniset $NOVA_CELLS_CONF cells cell_type compute
         iniset $NOVA_CELLS_CONF cells name child
 
-        iniset $NOVA_CONF DEFAULT scheduler_topic cells
-        iniset $NOVA_CONF DEFAULT compute_api_class nova.compute.cells_api.ComputeCellsAPI
         iniset $NOVA_CONF cells enable True
+        iniset $NOVA_CONF cells cell_type api
         iniset $NOVA_CONF cells name region
 
         if is_service_enabled n-api-meta; then
@@ -714,8 +714,8 @@
     if is_service_enabled n-cell; then
         NOVA_CONF_BOTTOM=$NOVA_CELLS_CONF
         screen_it n-cond "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-conductor --config-file $NOVA_CELLS_CONF"
-        screen_it n-cell "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-cells --config-file $NOVA_CONF"
-        screen_it n-cell "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-cells --config-file $NOVA_CELLS_CONF"
+        screen_it n-cell-region "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-cells --config-file $NOVA_CONF"
+        screen_it n-cell-child "cd $NOVA_DIR && $NOVA_BIN_DIR/nova-cells --config-file $NOVA_CELLS_CONF"
     fi
 
     if [[ "$VIRT_DRIVER" = 'libvirt' ]]; then